The classes at Cal are like none I've ever taken before, and I've had the opportunity to attend several diverse institutions. Even my easiest "cake" class is a rich tapestry of information and provide impressive historical context to the rather flimsy subject of study. I have been extremely impressed with this professor all semester. My most difficult class tends to expect the student to be very self-motivated in learning the material.The professor seems hesitant to explain it in too much detail or example, wanting us to have to work to figure it out. I've found this both extremely frustrating and enriching. I've (perhaps masochistically) signed up for one of her classes next semester because I'm drawn to the challenge of mastering her teaching style. My third class is a giant lecture with hundreds of students and a prominent professor. She is a very moving speaker, but I've found it difficult to navigate her course due to the highly subjective political stances she takes and her over-willingness to bring them into the classroom. I feel that professors owe it to their students to keep their opinions to themselves in introductory classes, at least. She seems to be much less of an actual teacher than a "celebrity personality".
As an English major, my classes are pretty laid back. I have a lot of readings (about a book a week), but not much in the way of actual assignments. I have maybe two or three papers due a semester and a midterm and final per class. The classes themselves are primarily discussions on what we read. They are a lot more in depth than what we did in high school, that's for sure. A lot of what we do crosses with other disciplines like history and cultural anthropology because we have to know the context in which something was written in to understand the motivation in which the author wrote it or some other such nonsense =)
This all depends on your major of interest. I, for example, am an Economics major. My requirements are five electives, and a few core classes, like micro, macro, and econometrics. At the moment, I am taking a course at the business school, a core economics class, and my senior honors thesis. These classes are all very interesting. If you don't think your core classes are interesting in the least, then you may want to reconsider your major. Discussions are primarily dominated by those who want to engage in the material, and it is wise to do so. Retention is key.
Some are huge, some are small. All huge classes have discussion sections. Almost all are very rewarding, with interesting and motivating world-class professors.