It's good, the story-line is a little weak (as at the end of the day it's the same as racing except one-on-one most of the time) but I definitely enjoy it.
If a Mario Kart style race is what you're after, this is what I'd recommend. The power-ups are pretty good (rockets, cannonballs, speed boosts, teleport (to name a few!)).
To add to Tiki Towers, it's one of those games I play when I have just a few minutes spare and not enough time for a race etc.