If you've played the original Cars, then this is more of the same. It's really more of an add-on than anything. The graphics haven't changed, the maps are near identical, the controls are just as bad.
Here are the main points to keep in mind. a)Kids will love it. b)Achievements are easier this time around (around 6 or 7 hours to max it at 1000/1000). c)Controls for the monster truck levels (thankfully only 3 races) suck. And I mean WAY worse than the rest of the game. d)Fetch quests are easier.
It's not a terrible game by any means, just not a really good one either. If you have kids, love the Cars movie or are an achievement junkie, then it's a definite rental.