If you've played Micro Machines or Mashed on PS2 then this would be the next gen version of it. If you're into multiplayer gaming (and I'm incredibly disappointed in Microsoft, why have a console with up to 4 controllers and only make single player games?) and want another party game that isn't Lips or Rock Band then give Blur a whirl.
Take a car (and they are actually real models), take a track, throw in some power-ups and it's like Mario Kart 64 all over again. The conrols are simple so that anyone can pick up and play, there aren't too many powerups so you get used to them very quickly, get 4 friends together and you'll be laughing and trash talking each other for hours.
Aside from racing there's also a destruction derby mode so if you just want to smash the fenders off of each other then take a break and show your mates who's king of the controller.
And of course don't forget that you can take the action online as well.