There have been more than enough reviews already, but id like to put some of my points which have not been discussed in other reviews...
being a fan of mr. bachchan myself, id rather not compare this movie with the original. a remake has been made to remove all the cons of the original movie and put forward new ones. now I believe all those who are reading this review have seen the movie, so ill get into the story a little bit.. farhan akhtar has changed the story to a grat extent, so youre not going to see what you saw 28 years ago. the original was basically an action flick, while this ones a suspense thriller rather. it has lots of twists, including the biggest one in the final 30 seconds of the movie.
I think some roles were not given full justice. like, jasjits character was not required this time (considering the twist involving vardhans character). and maybe kareenas and ishas roles should have been longer, rather than srk all the way.
after watching the movie twice, I can say that farhan wanted the audience to figure out the end themselves, with reference to a couple of dialogues along the line (e.g. don ko jangli billian pasand hain, and the most important one - don paan nahin khata, and a few more, but id rather not give away the spoilers). but it was the directors mistake that he didnt really let the audience know that they were to solve the case right during the movie.
a bit of comedy would have made it look better. I can remember only 2-3 scenes (like maa ki baat sunni chahiye thi and the scene in which srk says to desilva kahin aap hi nikal liye to?)
now the good points. shah rukh has proved that hes better in roles like this rather than the sappy lover-boy roles, and boman irani has shown some brilliant acting. not to mention FAs quality direction.
the twists in the movie are mind blowing. they kept me (at least) on the edge of my seat even when I watched it for the second time. so hats off to the editor and the cinematographer. and yes, the background score was one of the plus points.
edit: im looking foward to a sequel!