I thought the movie was OK, but I don't think I can give it a fair assessment because I kept dozing off. I have dozed off in only three other movies in my life (The Seven Percent Solution, The Hudsucker Proxy and Rugrats in Paris, if you must know!), but I can't tell in this case if it was Inception's fault or just the fact that I hadn't had enough sleep the night before. It did seem like there was a long stretch in the middle, where JGL was fighting with somebody or other and LDC was off doing something or other, that contained a lot of action but not much else. But again, that might have just been me. As Clyde points out, it requires that you pay close attention, and I wasn't in good shape to do so. I might try it again sometime.
Memento is one of my favorite movies of all time, though. Just a notch or two below you know what.