There are thousands of classes available every semester. Some courses are taught by multiple professors and they all range in difficulty. There are often classes that will never be taught again, or new classes being offered for the first time. Check out schedule.berkeley.edu to search for Fall 2012 and Spring 2013 course offerings.
Some have been very easy for me. Some have been very hard. It all depends on what your definition is. I have spent 3 hours studying/reading for a class for the entire semester just to pull off an A-. I’ve also spent 3 hours TOTAL on another class and got an A+.