My first impression: IRRITATING CAMERA WORK. Yes, I mean it. In the name of technological advancement, Ghajini gives you sore eyes. I watched it on the original DVD, and the print was very good. I don't know what the theatre audience felt, but I was irritated. The jump cuts and camera movements for no reason at all don't help you create the right effects.
Aamir Khan knew he had a weak script and too many flaws; so he decided to go all out marketing the movie. I did not think it was all crap, and found Aamir doing justice to his role. But there seemed to be no sense of time in the events. Was that intentional? Could be, as Aamir's Sanjay had lost sense of time and the director wanted that loss to seep into the audience's minds as well. You never know waht thinking goes into film making these days. Asin's character was hard to accept (as some of you have already pointed out the flaws in her characterzation), and Jiah was neither here nor there. Pradeep Rawat, the man (Deva Singh Sodhi) who opened the innings with Aamir's Bhuvan in Lagaan, gets a huge role: the film's title role. He should consider himself lucky, because all he had to do in Ghajini was blurt out a few angry words in Hariyanvi style and hit people on their heads with a rod.
The romance between the lead actors could have been better written: that would actually moved the audience. But the director was more interested in seeing Aamir build his body and do the Tarzan cry.
I give it 2.5 on 5, only because of the novelty of the story and Aamir's sincere effort.