It's reeeeeeally repetitive.
The cars you control are usually too fast to control well, so in order to not lose a lot of speed in curves there's a drifting mechanic where you stop accelerating for a second, then drift a little and then accelerate again. Mastering this is vital to success in the game, but it is also very intuitive. There's also a way to do this with the touch screen, so newbies will get used to it, but the drfting is intuitive enough for that not to be needed.
You can set your car to manual or automatic transmission. As far as I'm aware, there's no benefit of using manual, and it's harder.
The game has two other very important concepts: nitro and slipstreaming. Nitro is used for occasional boosts, and you have to charge it by drifting. Slipstreaming is placing yourself behind a car, so your car will boost its speed.
The gameplay controls perfectly, and feels great thanks to the slide pad.
10/10
Presentation: The presentation is great. The visuals look really good, but not perfect. When you play in 3D, the depth is incredible, and everything looks great and real, but it's hard to keep the sweetspot.
The sound isn't too great, and it's very repetitive. The ability to import tracks from the SD card should have been added, but the sountrack is not too bad.
9/10
Replay Value: The game has a lot of replay value, with lots of tracks and modes. The lack of online multiplayer or even download play shortens the game's life a bit, but you can race to get money and buy stuff after you beat the game, and beating the game will take long anyway. There's also multi-card multiplayer and a streetpass functionality where you exchange ghosts, but both are hard to do.
7/10
Fun: The game is not very fun after a while. It's too repetitive. You'll be playing the same tracks over and over again.
4/10
Overall: A good game, but not worth its price, and lack of online hurts and shortens its life. If you find it cheap go for it, but otherwise, look somewhere else.