For $10, it was a pretty good buy.
That thing, ladies and gentlemen, is the track editor. Once you get through the few races that are given to you, you unlock everything in the track editor, and should have gotten a feel for the physics of the game.
The track editor adds an incredible amount of replay value to the game. I've made several tracks, and pushed the track editor to the limits with things like half-pipes (made out of several rows of track, though that really screws with the AI, since they think they're supposed to race along it), massive, MASSIVE loops, jumps, and completely vertical sections to (unfortunately) the height limit of the game. Oh, and tracks that are hundreds of miles long. :P
All in all, I'd say buy it if you see it in a bargain bin somewhere, as it's basically F-Zero with whatever track you imagine.