Sometimes when you have had a bit too much of reality, any fantasy seems worth the sell. Rockstar in that sense is not just any fantasy though. It is something that can be believed in parts. If you have a different story to tell, it will surely keep one occupied for most parts.The songs blend in beautifully into the story. And you realize that it is fair to have Mohit Chauhan sing all of them, keeping it consistent with Ranbir's voice in the movie. This is commendable in a world where Akshay Kumar can end up with Rahat Fateh Ali's voice without anyone's bother.
There was a certain potential in the film, which if had been realized fully, could have become a poster film. Poster film is one that would make you wish you collect a poster and frame it, some years later. It had that kind of an art to it, specially the still shots and slow-mo. The DOP (director of photography) has left his mark.
If one cuts the hype around it, has their own small list of favorite songs sitting in anticipation, and appreciates the classic Imtiaz Ali first half humor, they may not be as disappointed as certain reviews are making it out to be. It does appear, though, that there has been some serious editing, in which they have probably cut out something relevant as well.