trusteft: FFS, couldn't GG put on sale S&SASR last week? I bought it from Steam.
Anyway, if you like kart racing games, it is a very good one and well worth the money. I played all the EASY level grand prix(prixes?) without much trouble, but then on Advanced (there is one more for 3 in total) difficulty the game gets hard fast. Basically if you don't use bonuses and turbo from drifts most of the time, you are not going to win a single race. Thankfully it is a good enough game I don't mind.
What I am trying to say, get it. Just a warning if you want to play online, you can't. The PC version supports multiplayer only as splitscreen 3 or 4 I don't remember, players.
So if you got to have online, get the 360 or PS3 version instead.
I got it as part of the Sega Mega Pack sale that Steam ran last week. So far I've played it far more than all of the other games in that bundle (bunch of Total War stuff, AvP2010, some other stuff) combined. Currently going through Expert Grand Prix as Sonic, getting first place in a race takes skill, knowledge of the course and luck with the other racer's items.
$11.98 is quite justifiable if you like arcade racing and/or kart games, even though there's no online MP.