Lottenbach is a great professor overall. The reading isn't that important, since he explains the material so well (which is funny because english is his second language). If you go to class, take decent notes, and listen well, you should have no problem with the essays. As other people have mentioned, he says "um" just about every 3rd word (I think he said about 10 ums in a row once), but it didn't really detract from his teaching since he keeps things very straightforward generally.
As a senior philosophy major, I took 21 for fun (yeah, I'm a bit of a loser) this past quarter with Lottenbach. It's a relatively easy class if you already know your stuff as a philosophy major (finding/formulating/analyzing arguments, writing philosophy papers and exams, philosophers, etc.), but it is a difficult class for those with little philosophy background because Lottenbach is a rather poor lecturer. Don't get me wrong, the man is a genius, but he says "uh" "right" and "so" about 237 times each per lecture which can get distracting, and, more importantly, he takes the most roundabout ways to answer the simplest of question (which my non-major friends found confusing), making it difficult to understand some of the material. I guess it also depends on your TA, go for James or Mandel, those guys rock. In addition, Lottenbach assigns rather obscure authors (Descartes was the only commonly known one we read), so if you're looking for a good introductory course so you can sound smart and talk about those philosophers all your friends know only by name, this isn't it. Lottenbach's expectations are certainly not high, but his lectures are rather boring, his answers to questions obtuse, his speech distracting, and his assignments obscure. All in all, not the most difficult class on paper, but rather hard given Lottenbach's style, especially if you aren't a major. Like I said though, he's a genius, so if you want to put up with his downsides to learn from someone who's read all the material in French, Latin, Greek, German, Italian, or English and basically seems to literally know everything, then take him, but be warned, Lottenbach's speech and way of answering questions makes things hard.
Prof. Lottenbach PREPARES for lectures (I see him in his office, through the hazy glass, pacing/practicing). He is extremely competent, thorough, and engaging. He simply knows his stuff. He offers historical background to the ideas he introduces without making it a survey course. He's enthusiastic after class hours also. Just make sure you're interested in the answer, because the man will talk and talk. I certainly hope he stays at UCLA a bit longer. UCLA can definitely use someone with his phisosophical background. Simply stated, he teaches philosophy well.
Prof. Lottenbach has to be one of the best philosophy professors at UCLA. He is extremely intelligent and knows how to teach philosophy really well. He makes things clear enough so that students understand them, he allows time for students to ask questions so that he knows that we understand the material, and he is an extremely FAIR grader. I would definitely recommend him to any student interested in philosophy.
After taking Lottenbach I realize that our philosophy needs much more improvement. I wish all teachers in our department learned from him. He is informative, insightful, opinionated... I like that. Furthermore, he is very intelligent and fields questions from students with ease versus the way other philosophy professors...by answering questions with vague answers. (If you are a philosophy major you know what I mean) Personally, I was really discouraged by our department before I took him. I am glad that we have diamonds in the rough like Hans. Take him. He's not easy. But he is fair, willing to talk during office hours, and makes every attempt to answer your questions. Peace.