Objectively, its average!
There are way too many flaws for it too be considered great... and way too much sensitive realism to be considered poor. That is I am afraid the reality.
Is it the ultimate feel good movie... well thats what critics here in the west are calling it. To me, no way, not even close! Go and watch Jo Jeeta wohi Sikander, for heavens sake! I dont know how it will fare at the Oscars, but anyways who in India cares about the Oscars. They will wanna give Ghajini an Oscar, if they could.
Right back to the review. The biggest flaw I found was Casting choices. The hero Dev Patel looks like a 18 year old kid at best. He is not epected to be that young for the story to truly do justice. A more mature actor would have been able to do a lot more justice to the complexities the guy is a witness to. His elder brother's part too could have been better demostrated by an elder more mature actor, rather than a 20 year old looking guy.
The movie's strongest part is the first hour, when the hero remembers his early childhood. The little children have acted brilliantly; way better than their older selves. Its not a must watch, but not a bad watch either.
And finally the stuff about Amitabh moaning that the movie potraying India in poor light is strange. He really needs to concentrate on acting. Thats what he is best at.