I was C Session last year. Basically, I was really really pumped to go, but a little apprehensive at the same time. I wasn't sure what to expect, but I knew that I was definitely applying. I think the most valuable thing I learned there was that not everyone there was the stereotypical definition of "military", whether they were upperclassmen or rising seniors (like I was). In fact, the most hoo-rah people seemed to be some of the guys in the elements around me. Doolie-for-a-Day was awesome -- not because it was tons of fun or made me think that Basic will be tons of fun, but because it showed me that I really could get into the whole teamwork, hoo-ah hoo-ah atmosphere when I wanted and then turn it off when I was done (hopefully that stays true after this summer!) something I really worried about. Like, would I become some military "joe" (or "jane" rather) if I did attend the Academy? Now I'm pretty sure I won't...
Soooo, it was really a great experience. I learned a bit about what the school, military, and athletic aspects will be like, and I learned (most importantly for me) that these were people I wanted to spend the next four years with, with the exception of a few, but that's every school. Have fun and good luck with applying next fall! Get your app in EARLY!