Track creators are what make a game fun.
I bought this game used at GameStop for $6, and for the hype it's received, I'd say it's worth it. A $6-$10 budget title is all I need to keep me cheaply entertained, and it's a good time waster.
I spent loads of time screwing around with the track editor, there's just so much you can do... after you beat the game and unlock everything for it. The track editor from the beginning starts you out with not much you can do... Choose a location, lay down a twisty, near impossible track, and race it. You can't add anything fancy to it until you beat the game. But after making a 193 mile long track, you really don't want to do anything to it anyway.
Another bad thing about the editor is that if you screw up a huge jump and then build more track that's really awesome after it... because the track is unplayable from the jump that you built, you have to erase everything you've done up to that point. There's no going back and editing a track in the middle of it.
The main game is kind of unfair, in its "second place is NOWHERE in sight, yet 5 seconds later they zoom ahead of you and stick there." It really seems that the AI has an unfair speed advantage over you. Watch out for that Bethany Robinson, she'll get you every time.
The sound is okay, if you like electronic music like I do. The soundtrack is okay, but I'd suggest turning the music all the way down and listening to your own stuff.
So, overall, I'd say the game is still just plain fun for $6-$10, mainly because of the track editor and the bizarre stuff you can do with it. I'm not one for "graphics over gameplay" like most are, I'm for them both equal.