I've taken classes the past three summers, and find that summer classes are much easier for me than regular semester-length classes. You're into the material every day, for a couple of hours, and it's only for about a month. This makes it easier not to forget stuff over the course of a semester, and you learn more because it's in your face all the time. I had Organic I and Physics I first summer session inf 2004, and Organic II and Physics II the second summer session, and did fine. I think I got more out of the classes in the summer than I would have if the class was over an entire semester.