Decent. It was worth my $5. I would have been willing to pay slightly more.
The graphics were okay, but not the best they could do. You'll recognise a lot of the textures and environment styles from Rayman 2: the Great Escape, which does actually help to bind the game more closely to the previous ones. Some details have actually been put into the racing and battle areas, but you can really only notice them unless you take the time to set up a game where you're the only one playing and just take a look around. These details aren't something you notice as you're in a serious battle or race game, but they are there at least.
Also about average, though I did actually enjoy some of the music themes they had going on. Some of the character themes were a little annoying, but all the more better to annoy your friends as you pull ahead of them in the race. You might recognise some of the sound effects from Rayman 2.
It was fun at first, and well worth the money I paid for it ($5). It does get boring after a while if you've got no one around often enough to play against though, but it's mainly created for multiplayer aspects, so that is expected. It's also good for some kind of harmless electronic stressball that I'd recommend for anyone who can't handle too much blood or guts. It works. I didn't experience any of the so-called "control issues", though it is slightly difficult in battles with a game pad. (I'd highly recommend mouse and keyboard for that.) You can get used to playing with a game pad after a while with enough practice, and practice is something you can do.
I did find a few, and the game seems to be slightly unstable from time to time. This is especially true if you set the game for 16-bit color mode.
It should be really cheap at the moment. It's a good buy if you find it for a decent bargain or something. If you're looking for some kind of decent single-player challenge battle though, don't bother. It does get boring after a seemingly short time when it's just you playing all the time.