A pretty good movie. Considering its a Hindi movie, where run-of-the-mill mushy movies or overly macho gangster movie typically works, this is much more well made and well acted.
The story itself is not very deep, but it has been adapted to a very taut screen-play with excellent editing and direction. All the actors do justice to their roles. Although Vishal Bharadwaj is said to have stated that the movies is a tribute to Quentin Tarantino, this movie is neither dark as QT's nor have the funny lien that a Guy Ritchie's movie has - the other guy's creations with whom this has been compared with . It could be placed in that genre with multiple story-lines interwoven giving a good enough time, but taut, for the characters to develop.
It does hold the viewers in thrall and doesn't overly insult their intelligence by going overboard on emotions (except, probably, for the Mikhail's role). Shahid Kapoor is quite brilliant in both the roles - he was quite a revelation; and has shades of Tom Cruise in some of the scenes. Priyanka Chopra as Sweety is different and has done justice to her role, rather than just being a doll.
If you are a fan of such a genre, watch it - you'd enjoy it. However, I'd place this movie a notch below to that of Omkara, which had a bit more of heavy cast with a higher star value.