I had a very similar experience. They showed us a sneak preview of it while I was in college and when it was over I wondered what the hell I just watched. I didn't think it was funny, I didn't think it had a story, it was just 2 hours of my life.

A couple years later for whatever reason I decided to give it another try and I liked it a little bit more, but I still didn't think it was good. It took about three viewings for everything to click and then I thought it was a masterpiece.