I thought Renfrew was a good instructor. He spent most of the class going over example problems. As for the exams, the material was very straightforward. He always gave out a previous midterm/final and practice problems. Study these and similar problems and you should be fine. There is partial credit given for questions. The homework each week was a couple problems. It would have been a lot easier for me if I had a study group (form one if you can). I ended up with an A in the class, not too difficult if you have taken calculus before.
For 170A: Very good professor. Professor. Renfrew used fixed-point cutoff to assign grades rather than typical curve policy. However, it maybe good for people who are not top students. The midterms for math 170 were pretty hard, but he ended up giving easy finals and curved up a little bit. Overall, his course is worth taking.
Pretty good professor, very different from those negative comments. He did give us a very hard second midterm, but he lowered the total points from 55 to 50, and he assigned very few points for the hard problems. The final was super easy. I spent 40 minutes and handed in my paper without double-checking, and I still got an A.