Castella is a great math professor. Very clear, helpful lectures.

The tests were challenging, largely because of the time constraint, but very comparable to the homework.

Castella is very clear on what you should know for the tests. If you study the practice tests he provides well, you are set for the actual midterm/final! There are no curve balls! The only downside is, everyone thinks this class is easy, and if you make a silly mistake on the test, it can set you below the curve quite easily. For the second midterm, I got a hold of a past midterm and did it over and over again, and got 100% on the actual midterm. Just don't make silly mistakes and you'll be good.

To put it simply, Castella is a great math professor, and he is the best of the four I've had at UCLA. He does have a Spanish accent, but I thought he was still understandable. That aside, his notes are quite clear, and he focuses a lot on examples. He made linear algebra computational rather than focus on a lot of geometrical understanding and theorems (a huge contrast to my nightmare with Gilmore for Math 32B-good thing she's not teaching here anymore). He is fair in his exams although the midterms were time-constrained. I did well on the first midterm, but because I had an LS midterm on the day before the second midterm and due to stupid mistakes, I actually did really bad on the second exam even though it was fair in retrospect. However, his policy of dropping the lower midterm saved me, as I got 100% on the final (yes, it is doable for a math class) and I got an A+ in the class. For the exams, focus on his practice exams he gives you, as the textbook for the class was horrible. His excellent and clear notes were sufficient. On the first day of class, he seemed really serious and in a bad mood, but I learned that he just has a serious personality, so don't be scared to approach him during office hours, as he is helpful. He also assigns practice problems from the textbook, and although some were irrelevant to do looking back at the practice exams, I recommend to still do them if you have the time. His homework is not from the textbook, so my advice is to work on it with a group of friends/classmates-I did this and it helped us understand the material even more. Overall, I recommend Castella, as he is one of the most straightforward math professors you can get.