Many people including the professor himself said that this class would be one of the hardest cs classes here, but honestly, it did not live up to that reputation for me. There were 4 labs + 1 warmup lab which were not too hard nor time-consuming. A very nice break coming from 35L( I think I spent maybe a quarter of the time compared to that class). I don't know if the grade distribution will get posted, but it was as follows for this quarter(from professor but w/o some regrades probably):
A+: 5
A: 37
A-: 53
B+: 29
B: 23
B-: 8
C+: 1
<C:1
There was no curve, every 5 points you lose, you go down 1 mini-letter grade (e.g. 95-100 A+ 90-95 A, etc.) If you want to succeed in this class, it is basically all about doing well on the exams, which I really don't have much advice for. They were hard to study for and pretty difficult, so I think the disconnect between the relative ease of the labs and the difficulty of the exams kind of threw people off. The median for the midterm was 75 and for the final 77.5 (basically translating to an A- final grade).

--Course: Most of the issues that I have with Prof Xu are because of cs111. It is a poorly designed class and any professor that has to teach this class will probably get bad reviews
--Lectures: Prof Xu was not the best lecturer. He mainly just read off slides and was not very engaging. The information provided was decently easy to follow and useful.
--Discussion: There is not mandatory attendance but YOU NEED TO ATTEND DISCUSSION if you want to understand the projects. Find the TA that gives the most hints and attend their section
--Projects: The specs are always not easy to follow, and discussions are needed to understand them. They were usually pretty hard and took a good amount of time
--Exams: The midterm wasn't too bad but the 2 hour time restraint was tough. Prof Xu was accommodative for the final and gave plenty of time.
--Tips: The textbook is really good and the best way to absorb the content. Go to discussion to understand the projects.

This class sucked but the Professor was really nice and it was NOT HIS FAULT THAT THIS CLASS IS BUTTJUICE. He made the first midterm quite difficult but made up for it with a very simple final that had a really high average. He listened to student concerns and was willing to try and change stuff to accommodate students and did as much as he could MID QUARTER to change the class to make it better. He said he was actively trying to fix this class but there is only so much one professor can do! I liked him a lot as a person and I do NOT get the hate at all.

Everything I learned is this class was solely due to the readings and the projects. I did not learn anything from Harry. His lectures were dull and entirely failed to engage me. He doesn't explain the concepts well and he isn't the best at answering questions.

With that being said, this class was not that bad. The midterm was pretty easy and the questions were rather straightforward. As long as you are able to do well on the projects and actually do the readings, you can get an A. There is a decent amount of work (readings + weekly projects), but honestly the class is easier than 35L and the material you are learning is more interesting.

Harry isn't the best pick for this class, but in the end you can pretty easily learn everything on your own.

Start the projects early.

This class was a disaster. Yes, there was a lot of work (a ton of readings and projects). I knew that going into it. But that is not the problem with it. The way everything was handled in this course was atrocious. It seemed like nobody cared at all about us. At the beginning the TAs would change the project specs 5 comments deep on a piazza post from days ago without notifying the rest of the class of the changes they made. The grading scripts for these projects are whack. Most of my friends had this issue where our code appeared correct, passed a sanity check which should verify that your code will run correctly (not get all points, but at least run on the grading script), but we lost a lot of points because the grading script had issues running the tests. Some of the TAs were unresponsive with regrade requests. Harry then didn't do a great job lecturing either. He reused the slides from a previous professor. The midterm was really easy, but because of one small mistake I got below median (literally 1 mistake). Because of the Coronavirus, our final was made optional. People who actually took it said it was impossible, so be warned of what may come in that regard. As well, I don't know what Harry's grading scheme was, but I had a solid A percentwise and ended up with an A-, so he does some form of readjustment not necessarily in best direction.

Xu is a new professor at UCLA so he uses Reiher's slides and doesn't seem too familiar with them. Lectures are sometimes confusing and I find it hard to pay attention to him. The entire course website is copied from Reiher's (so same readings) and the links didn't work. He did not reply to questions on Piazza but the TA's did... most of the time.
With all that being said, he's probably the easiest professor for this class. The midterm was similar to Reiher's, but the final was very different. He gave a pretty comprehensive list of areas he'd test for for the final and I crammed for it but I feel like I shouldn't have done that because the final was totally different from what I expected anyways. It's easy in the sense that you can get away with not really reading the entire textbook (which to my understanding is a requirement to do well in other professors' classes). But you need good intuition with the material.
Overall, the professor is a nice guy.
Like other reviews for CS111, I recommend going to Zhaoxing Bu's discussions if you want to do well, but not necessarily to learn.

This class was so frustrating. Harry half asses his lectures HARD. Imagine you're back in high school, and you're watching a group present their project. One person made the slides and another person, who did not help with the slides whatsoever, has to present the slides for credit. That is what Harry's lectures feel like. All his slides are a stripped down copy from other professors' (from entirely different universities) slides. It is painfully obvious that he does not read the slides before the lecture because he will stand up in front of the class, read the slide, try to figure out what the hell it's saying, and then give a poor and usually faulty explanation for it. Not to mention, he usually cannot answer people's questions because he cannot understand what people are asking, even if it's a clearly explained question. I got second-hand embarrassment watching him hear a person talk, and then misconstrue their question so badly (even after they repeated it and rephrased it) that they eventually dropped it. For all of his mediocrity in lecture, Harry still made difficult tests that were often calculation-heavy and cherry-picked (once again) from other professors' tests, to the point where much of the stuff was only tangentially covered in lecture and never to the depth required to answer the questions.

His projects were easy only because he used Jon Eyolfson's. His TA, Sicheng Jia, was a godsend and the only reason this class didn't send me over the edge.

If you actually want to learn something in lecture and not pull your hair out, do not take this class with Harry. I feel as though I wasted my time and money.

The TAs carried this entire class while Xu seemingly put in 0 effort. As past reviews have said, his lectures are completely useless. He couldn't even be bothered to write his own practice questions or midterm/final questions. He seemed to not care about the class at all, which made it very difficult for students to be invested in the class too.

After the midterm, most people stopped attending lectures/doing the readings because it just seemed so futile. The labs do take up a decent amount of time, but if you have a good TA, they may provide a bunch of starter code that would otherwise make the labs impossible.

If you want to actually learn the material or want a professor who genuinely cares about your learning of this class, do not take this with Xu. The curriculum is in serious need of revamping (we had to spend $100+ on a Beaglebone for just 1 lab with 3 parts), and taking it with a bad professor will just further worsen your experience.

There were honestly a lot of missteps in this class. But Harry Xu undeniably cares—a lot—about his students. That's really all I have to say. Take it with him if you can.

I honestly don't know why everyone is complaining about this professor. I thought that this was an excellent, engaging class and really enjoyed lectures. The difficulty of this class did not live up to its reputation as the second hardest CS class at UCLA; labs compared to 35L were very easy (taking max 6 hours each, probably less for some of them), and the TA's discussions made it very clear as to what needed to be done. Although the professor did use slides from other universities, I thought he knew he was talking about and could convey the information in an interesting and knowledgeable way. When people were confused, he took the time to go over the material more thoroughly and answer any questions they had; he was also willing to stay after class a lot to answer any questions (sometimes staying for almost half an hour after class). Also, he was very eager to accommodate student requests, such as more practice problems (though admittedly these weren't always reflective of the types of problems he would ask on exams), COVID accommodations (lectures were both live and on zoom, and he also held an online final for those quarantining), etc.
I also thought it was great how he explained everything from the ground up. Although Bruinwalk seemed to think that Professor Reinman for CS33 was a great professor, I personally found him really confusing (and consequently the class really hard) because he would never explain some of the technical terms that he would use. In contrast to this, Professor Xu would define his terms when he could, and when it was too inconvenient, he acknowledged that sometimes he would use a term before defining it, making it clear what he expected you to know and not know at particular points in time. Thus, I found this class to be of similar difficulty to CS33 even though it was supposed to be much harder.
While Professor Xu's exams were tough, I thought they were fair. The midterm was definitely a time crunch -- I didn't complete a lot of it and ended up getting a D- on it. However, with a little bit of consistent study and practice problems, I managed to get an A- on the final. While the problems on the midterm/final are more hands-on than you would expect (page tables drove me crazy), I thought that they were an extension of what was taught in class. For some of the problems on the midterm/final, the professor spent a lot of time in lectures going over similar problems, and sometimes straight up told the class that a certain type of problem would be on the midterm/final; for others, you needed to do a few practice problems on your own so that you knew the different ways those problems could be asked. Extra studying for midterm/final problems is definitely needed, but if you do that then you should be in a good position for the exams.
I will say that there was a lot of contention about the grading/answers of the midterm (there were some typos/expectations not clearly conveyed/randomly changed definitions of stuff), but the TAs and the professor made sure to give points for each way a question could be interpreted.
Professor Xu also said at the beginning of the quarter that he decided not to curve the class. I think I saw some other reviews complaining that there was no curve, but they also neglected to mention that the professor had a very generous grading scale (95+ = A+, 90 - 95 = A, 85 - 90 = A-, 80 - 85 = B+, etc.). This grading scale probably helped more than a curve because I believe people did very well on labs and didn't do too badly on exams (which I think had an avg of 72 and 77 or something).
As others mentioned, Sicheng was great. Highly recommend him.
TDLR: professor was great, I had a lot of fun and this class wasn't too much work (no 20 hour projects!) and definitely was not the second hardest CS class (I thought 35L was much worse). But don't expect it to be too easy.