In terms of lectures, I liked Prof. Killip's teaching. I generally found him quite clear, and his lecturing style does have quite a bit of personality. My impression is that in terms of course content, we hit all the points, and then some; in particular, I appreciated how Prof. Killip would sometimes talk (both briefly, or to some length) about probability topics that may not have been in the course description, but were often relevant/important nonetheless. In terms of formality, I didn't find the class to be especially formal, though we did still do a fair number of proofs & convergence analyses. [A shout-out, also, to our TA James Hogan.] I did admittedly have some trouble following Prof. Killip during the last week of the course, while he was covering multivariate normal distributions; other than that, however, I found everything else understandable.

As far as homeworks go, though...woof. To play the devil's advocate, the homework was very helpful in getting a better understanding of course info and practicing the various concepts covered. Even certain ideas/topics that were only briefly mentioned in class, got a fair share of attention and expanding-upon in the homework; some of the homework questions also touched on more application-relevant topics, such as estimation and sampling. That being said, there was a lot of it. A lo-o-ot lot. The homeworks were generally 5-6 questions, very slightly computation-leaning, and took me maybe 6-8? hours on average. That alone doesn't sound too bad...except there were 10 of them, one a week (including midterm week + and week 10), which basically means there is no such thing as a break with this class. To be fair, we did get 2 homework drops; that being said, all questions were graded on correctness, and some of the homework questions were legitimately difficult. To rub extra salt in the wound, all homeworks were posted on Saturdays and due 9 AM the following Friday, which meant we actually had 6 days for each homework...assuming all the requisite knowledge had been covered, otherwise it was more like 4 days. To Prof. Killip's credit, he was generally helpful and did a good job answering questions during office hours.

As far as exams go, I personally thought they were okay. They thankfully weren't as difficult as the homeworks, and I found them to be fairly reasonable for the most part, though the timing was a little tight. We did have averages in the mid 70s for both the midterm and the final; that being said, I believe there was also a fairly generous curve. (I made some pretty dumb mistakes on the final, ended with a raw score of ~89%, and got an A.) As a side note, our class only had 15 people in it by week 6, which was kinda strange; I don't recall us ever having too many people, so it wasn't necessarily an attrition thing, but I can't say if the small class size ended up affecting grading somehow.

Killip is funny, smart, organized, and a great professor. I found his class to be incredibly difficult for some reason though. This was harder for me that 115A, 131A, and 131B to be honest. So if you are a pure math major just be careful because even though everyone says 170a is easy, it is still hard for some people. Also, killips homework was too freakin hard. I spent so much time trying to figure out some of the questions and most of the time I had no idea if I was going in the right direction since he makes his own questions. His midterm was easyish but it is very easy to make mistakes on the counting problems. His final was insanely difficult. He is obsessed with the bivariate normal distributions, which I dont think other professors even talk about. He tends to cover random things more in depth than other professors, but I am certain he has a reason for them. In the end, I still recommend the course since he still curves generously. Just don't be surprised if you are struggling on the homework

The homeworks are hard, which normally you would expect to spend a 5-6 hours weekly on homework. But the exams are generally easier than the homework.
According to the TA, Killip is the best professor to take to truly understand the material. "He teaches you 200% of what you need to know compared to other professors. So even if you only retain 50% of what's taught, you've mastered 100% of the material for 170A."

Would strongly recommend to go to his office hours and the TA's.