I saw this movie in 3D last week, the ticket sure was expensive (7 euros with a student discount!) but it was worth it. All in all, great plot, great design, photography, special effects. It's pure science fiction at its best.
However, for me it wasn't the best movie of 2009. That would have to go to 500 Days of Summer, a great film, it's wonderful how they picked up a simple script and turned it into something epic.