It's very good indeed. It's also one of these films with large enough scale special effects that it benefits from the large screen.
http://www.youtube.com/watch?v=z75o-F6ja2I&feature=related
I'm not sure how much I can say about the plot, without giving too much away. But suffice to say it's about dreaming, and stealing secrets from people whilst they dream. It quite nicely explores concepts of dreaming and reality, but at the same time manages to be quite a fast paced action film, with some spectacular special effects.
And it ends so beautifully too.
I think I really liked this film and I think it's one of the ones that you should make a point of seeing in the cinema. But take your brains with you.
Edit: Prequel to the film (comic)
http://movies.yahoo.com/feature/inception-comic.html