I definitely enjoyed the movie quite a lot. I believe it would be a good example for a "masala movie". Love, Romance, Action, Eastern, Sci-Fi, Thriller: all-in-one. And that with the most excellent dancer and "India's Schwarzenegger" Hrithik Roshan and former Miss India Priyanka Chopra as the two lead actors. And despite all the action scenes, the film actually is still cheesy enough to fulfill the Bollywood cliche :)
I also think it marks a new milestone in the area of special effects for Bollywood cinema. As a sequel to "Koi Mil Gaya", it definitely goes way beyond its prequel.