Okay. I'll speak from personal experience here. This is for 151B by the way. In a nutshell, Deutsch's lectures aren't the best, but the graded classwork and exams are very manageable. Lecture-wise, his handwriting was hard to read, and he would repeat what he writes without giving much context. Thus, it's super hard to digest the information, especially with the very algorithmic and computational nature expected of the material in 151B. However, if you need to take the class, what I advise is to truly take some time to sit through and understand the corresponding sections in the book deeply. His tests do not have unreasonably hard curveball questions, so you should end up thoroughly knowing how to do the easier derivations and how each method works, as well as advantages/disadvantages. I mean, I could tell that he's a nice professor too, as he offered to drop one of our midterms later in the quarter and curved pretty generously at >=85% being at least an A- (probably because the final had a median of 70, but in my opinion, it was pretty fair). All in all, unclear lectures, but manageable work and tests.

Amazing professor and very reasonable! Would recommend