I for one really like this movie for some reasons I'll go into late but I want to touch on why I think people don't like it. First off, there are people out there who just like to hate Tom Cruise. I don't understand it really. Second, Cameron Crowe I think successfully p***es off two groups of movie-goers with this film. The casual, relaxed, "not looking to think too hard" group of movie-goers are left confused when the plot takes a complete 180 at the end of the movie. And the deep, philosophical, mystery-fans are devastated when Crowe has one of his characters completely explain the mystery.
This is a good movie. And Tom Cruise does a very good job in it. I think it's probably his best performance from what I've seen all though I haven't seen all of his movies, or even a majority of them probably. The supporting cast is good as well. Penelope Cruz gives a solid performance and Jason Lee was enjoyable.
I like the story, and I think that's what Vanilla Sky is more than anything. It's a mystery, an adventure, and a romantic comedy, but it's mostly just a good story. And it has a lot of philosophical undertones to it, and many similar ideas and stories like this occur in historical philosophy. David Aames (Cruise) is the man that had everything he wanted, more or less lost it, was given a second chance with a catch to regain it all back, and in the end facing his demons and the full scope of what is happening, chooses reality, simplicity, and normality to see if he can finally find the one thing he could never get a grip on: happiness.
Many people were disappointed that Crowe laid out the complete mystery at the end. I think it's necessary. The audience then knows beyond a shadow of a doubt that David is aware of his circumstances and it makes the choice at the end all the more powerful.
And the music in the movie is great. It's probably what makes the movie as enjoyable as it is. Particularly, "Njosnavelin" by Sigur Ros, which is an amazing song.
All in all, I'd give it 3 out 4 stars. It's a movie with some substance for those who like to think things through, and a great story for those looking to relax. That "moderate" approach is probably why people dislike it so much because it isn't a full blown mystery, or a full blown love story. It mixes and matches different elements and genres.