It can be a depressing experience to research classes and find that nobody's had any good things to say about the professor. It can color your experience and help reinforce the fear and trepidation you might already have.
This is a thread in which we should say only nice things about professors. The things we write here shouldn't be back-handed compliments or ironic gestures. Professors you like and ones you don't like have good qualities. Let people know what they are.
George Bergman is willing to answer just about any question you ask him. He knows a little about almost everything. He is the fairest--not the most liberal, but the best at giving you credit for the knowledge you've demonstrated--grader I've ever had at Berkeley.
James Demmel gives incredibly clear explanations, and he's always so cheerful that boring things don't seem so bad.
Alexander Givental will give you valuable geometric insights into any subject you study with him. Sometimes he would say something that didn't make any sense to me at all, and months later it would come up in a different context and I'd get this wonderful epiphany connecting two seemingly-unrelated concepts.
Ken Ribet genuinely wants his students to do well in and enjoy his classes. He's terrific at getting to know his students, and he's very helpful in office hours.
Ted Slaman is incredibly patient. He'll explain something a dozen times if necessary, and he's got an excellent sense of when he's confused his class. He is also very funny.