I'm coming from a different perspective here, so take that into account. Having worked for BR in Southern California for a while now, they offer what I would say is the perfect class. The lectures are designed to review material in context. Most of what you learn involves applying concepts to questions and the art of analyzing questions and their answer choices. You will learn unique ways to think about the content and some unforgettable mnemonics. Ask any Berkeley Review student to draw the common sugars in any format (Fischer, Haworth, or chair) and you'll see what I mean.
If you want to see a class first hand, you should sit in on a lecture. It's an open invitation to anyone interested in their classes. So far people who have sat in and compared the BR classes to other courses all seem to end up choosing BR. Small classes with expert teachers, two of whom are the primary authors of some of their books, is pretty much unbeatable. Ask students what they think of Tammy, Todd, Spencer, Cecile, and Adam and you'll hear glowing praise. They are a big reason for the exceptional scores BR students have been getting on the new MCAT.
As docdoc points out, a majority of the students in the summer Irvine course are from UCLA and UCI. During the school year it is a lot of students who have graduated from all over (in the Fall class) and UCI undergraduates (in the Spring class).