The critics speak.
For what it's worth, I didn't see much in the film that hadn't been done better by Dark City, the Matrix* or Total Recall. The only hints that we have that anyone besides Fischer is a real person is the kiss between Ellen Page and Joseph Gordon-Levitt; it's the only actual moment of human feeling in the entire piece. Marion Cotillard is radiant and rises above her lines (the incantation about the train sounds dumb when we find out what it is), but imagine if Page had been a rival to her charms. The plot "twists" were all heavily telegraphed and easily familiar to anyone who's read Dick, Borges, the better Bradburys, or Poe. Would it have hurt to have made Saito Chinese instead and had a reference to Zhuangzi?
I think the final scene makes the whole thing obvious (remember: we don't know how Di Caprio washed up at the beach at the beginning of the film, which is a dead giveaway). That is a big disappointment, especially compared to Total Recall. Clearly, Nolan is brilliant--the film is gorgeous and visually inventive--but his talents are better deployed at adaptation than invention. In particular, Dark Knight portrayed a better understanding of ethical challenges and moral questions than Inception, which has none.