Bought the PS3 version for my brother for Christmas, & he's enjoying it. His negatives so far are that the game doesn't support the Logitech DF-Wireless steering wheel, & that it's too easy with all the driving aids on, & too difficult once you start turning them off (to be fair, he's not that good

..sssh!!)
I played a couple of levels a few nights ago, & it did seem like a lot of fun, & even with some of the aids turned off I didn't find it too difficult except for one snowy rally level that was a nightmare, but I think that's just part of the challenge. It was certainly better to play on immediate pick up than NFS:Shift 2, which I found the controls to be horrible even after half an hour of trying to keep the damn thing on the road.
For £7 I don't see why you shouldn't pick up Dirt 3.