Depends what platform you are buying it on. This video on YouTube compares graphics between each platform, the PS3 looks by far the worst (I have PS3 and PC and the PS3 is miles behind graphically).
Overall it's a very good fun game, especially online with mates you trust not to use the setup bug. I like the fact your XP goes down as well as up online.
The AI is mixed IMO. SP it can be really good fun, but MP it's poor. Co-op the AI switches off after the first race so you go about 5-10 seconds quicker a lap dependant on the track and your speed, and in a standard online race with AI they drive into you like they can't see you....I ended up on Sutil's head going around turn 1 & 2 in Brazil until my car slid off due to this strange AI behaviour.
Despite these issues, I love the game. DRS and KERS make it very fun, and the tyre deg also makes long races more interesting.