I thought the course material was fairly straightforward, and Prof. Willis certainly helps make it even more so. He's a clear lecturer and he's always willing to take questions during lecture, help out during office hours, and take suggestions from students about the course structure, which was key since Spring 2020 was remote/online.

The overall grade is: weekly homework (20%), two midterms (20% each), and the final (40%). Exams were fair, possibly even more so than the homework assignments, each of which always seemed to have one really tough problem.

In general, I'd definitely recommend taking 120A with Willis.

He was decent! (I took the class last year for four weeks with Petersen, and Willis is much better at teaching this course IMO). The dude's notes are insanely well written, but the homework can be pretty rough in some weeks and we don't really get solutions afterward from the TA so the learning experience from that is cut a bit short. I also say his explanations of class concepts were definitely not as good in the later half of the course, but then again the material is significantly more difficult at that point.

Tough class, but Mike is a solid prof. The lecture notes are gold. My only complaint is that we got some really tough homework problems and there were sometimes mistakes in assignments or misleading hints.

Math 120A by nature is a very painful class (just imagine all the tedious derivatives and cross products) as well as having a lot of things to memorized. Dr. Willis midterms always have about 20-30% just based on reciting theorems/definition and maybe 10% on conceptual understanding through true false. The homework assignments were not easy but with the help of TA and his class notes, they were manageable. The exams focus heavily on conceptual understanding and the calculation/algebra required were not terrible on the exam. On the final a brief formula sheet was provided, but for the midterm, need to memorize formulas.

Professor Willis loves to focus on conceptual understanding of the materials. That is to say, his lecture and exams incorporate a lot of these kinds of materials. It's overall a not difficult course, but the curve is also not very good.