Sebastian's lectures are hardcore and derivation-heavy, which I like a lot. He is very happy to answer questions and clarify things. The tests are not hard, and he would brief you before midterms and finals, which are not cumulative.

Good lectures, but does not cover all contents needed for homework so a bit confusing and need self study

One of the best! Very thoughtful, open to questions, wants you to understand and appreciate the material, extremely accommodating. His lectures can be hard to follow at times, make sure to ask questions about the proofs if you're lost. He's happy to clarify in office hours too. He'll tell you exactly what topics will be on exams.

I took 23, 24, and 104 with Prof. Streichan and he was a gem in all three. One of the few physics professors who you can tell truly cares about teaching and his students. His homework is manageable and exams are easy (in the context of the department, of course). Lectures can be derivation heavy, but he never fails to make the material digestible.