Fun for about two days...then you've beaten everyone, finished the story, and have nothing left but multiplayer.
With Carbon, they've attempted to remedy some of the complaints of earlier games, which is good, but in the end, the game is just too darned short to recommend. When I started playing, I found the graphics very nice, rivalling the first PSP NFS. Not bad, considering the severe difference in specs from the DS to the PSP. As well, the cars are very easy to control, but not easy enough to get boring; the control over the cars is good, with easy to manage steering and drifting. A nice sense of speed is conveyed, and the oncoming traffic is never too dense to be annoying. Lots of shortcuts in each track make for some variety, and the frame rate is smooth as warm butter, with only the occasional pop-up (when using nitro, usually).
So what's the deal with my rating?
The game is short short short. Playing it off and on over two days, I managed to finish the entire set of races, failing to be first only once or twice. They either made this version too easy, or just didn't have enough events to extend the life of this one. If you have friends with a DS, you can go multiplayer, but otherwise, this one has a short lifespan.
Even with all the bells and whistles of unlocking new items, it clocks in at under ten hours of game time....too short for the $35 pricetag.
So, although it *is* a good game, it is one of those games you may just want to rent, unless you spend most of your time in multiplayer.