As a fan of Haruhi, I could not have wished for a better movie. In fact, two and a half hours in to the movie, I was disappointed to find out there was only about ten minutes left. It was that good for me. All the adventures I wished happened in season 2, coupled with very interesting plot twists, new views on all my favorite characters, and superb animation make this my favorite movie of all time. If you ever have 3 hours free, you can not go wrong with this movie.
A bit of warning though, it is chronologically after both seasons 1 and 2 of The Melancholy of Haruhi Suzumiya, so there is a lot of character development coming into the film. I am sure I would not have enjoyed it so much if I had not come in prepared.