So much hype about Rajneeti being based on Sonia Gandhi's life - and so no truth in it. If you want to watch Rajneeti because you want to see Katrina playing Sonia, you could watch only fifteen minutes of the movie. That too when she delivers a five minute childish speech. And then so many characters in the movie die through the movie that I thought that by the end of it, the only people left would be the twenty-odd strong audience in the cinema hall.
On a serious note, the movie is a loose adaptation of Mahabharat - there's a Bheeshma (who, here, is not sleeping on a bed of arrows but is paralyzed.) and there's a Karna (the Raani maa's illegitimate child which was sent away and later raised by the family driver).
The strong point of the movie is the performances. Nana Patekar as the highly intelligent guide (the Krishna of the story) is AWESOME right from the beginning. Ajay Devgan emotes through his facial expressions - he gets the body language perfect. He is awesome. Arjun Rampal and Manoj Bajpai are both very good as the two wicked men. Arjun Rampal gets the cocky politician very well. Ranbir and Katrina, I felt, are just about average - as compared to the other actors. And it is, of course, not very surprising. The film is shot in and around Bhopal which looks apt for the setting of the movie. It was surprising to see Shruti Sheth in the kind of role that she has in the movie - especially since I have seen her in many of her candyfloss roles on TV.
However, there are some dialogues which look slightly strange/out of place - and one thinks whether the dialogue writer actually wrote dialogues for the TV serial Mahabharat. ('Yeh mera jyeshta putra hai.' is not something I hear in my day-to-day life.) The story becomes predictable once you get the Mahabharat connection. It drags in parts in the second half. The climax is quite ordinary. Also, I do not quite remember ANY of the songs right now - the item number is there just for the sake of being there. Katrina looks very good in the song though. By the way, Nasiruddin Shah is hardly there for ten minutes in the movie. (Side note: Katrina's saris are way too low for 'Sonia Gandhi/lady politician' image that she portrays.)
So basically, don't watch the movie for Sonia Gandhi rendition of Katrina. But that shouldn't deter you from watching the movie for it has many other strong points: Great performances by the actor ensemble and entertaining plot.