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.