I bought it for the rally races, but I'm loving the X-Game races.
The graphics are in a word superb. They are so good I actually sit through the replays of the event and races after your done. Photorealistic is a word that readily jumps to mind when viewing Dirt 2.
The game play is very good. I would definitely recommend a wheel if you can get one. It certainly takes the realism up a notch. Much has been said about the inclusion of the X-games license. I have to admit I wasn't a fan of it, but now that I've played it I really like the racing involved. Unlike rally racing where it's just you up against the clock, the X-game races let you bump and jostle with other cars. Great fun!
Now go get DirtY.