Ok, so I bought this for the girlfriend but actually quite enjoyed it for a while.
Unfortunately there isn't enough variety in the characters. Lightening McQueen has exactly the same stats as about 2 or 3 other cars. The ability to customize cars, E.G. increasing speed or turning ability, would have been a nice touch. As it happens, unlockable colours is the most that can be changed on the any of the vehicles available.
The racing controls made my fingers really sore. It wasn't just me either, my girlfriend didn't play the game for more than 15minutes at a time because it hurt so much.
The tracks vary from genius to madness. Its good timing jumps to clear obstacles and hit boost pads but its incredibly frustrating when a combine harvester appears out of nowhere and stops your car dead in its tracks.
The game doesn't last that long either. I'm thinking its perhaps aimed at a slightly younger / more casual gamer than me though.
Overall it was better than I ever expected a movie tie in to be and is the best Disney movie tie in game since Lion King or Aladdin...