If you didn't buy it yet, I would advise you to wait until it drops in price, because it's not going to take long until then (if it hasn't dropped already). That's the fate of artsy games. As for your questions:

Its best quality is probably that it isn't a Nintendo game. So if you despise Nintendo, there is a better chance that you will like this game. I honestly can't think of anything that this game does really well, but it isn't terrible either. It just feels average for the most part.

I haven't played the demo, so I can only take a guess that it is a good representation of the first half of the game where the problems aren't as severe. Things can get really hectic in the latter half of the game and annoying when your character pulls off a move you didn't want him to. There's a lot of frustration involved and the plentiful checkpoints and infinite lives serve only as a band-aid for this problem.

The problem with multiplayer is in the level design. By default, you need to forget about 20 % of the levels in this game, because they really are for a single player only. In the remaining levels you need to accept that you most likely won't be able to get everything, because quite a lot of stuff is timebased and the more players there are, the less likely it is that everyone moves at the same pace in those sections.

The main goal of the game is to collect Electoons. Half of them are hidden in the levels, the other half is gathered by collecting a certain number of Lums (these can be timebased) or by doing speedruns. I am not sure on the required numbers of Electoons you need to reach by certain points of the game in order to play the next level, but I think it's possible that in multiplayer you need to go back to previous levels or play some singleplayer.

Wiimote, Wiimote/Nunchuk or Classic Controller. I recommend the CC option, because it offers both a d-pad and a stick, so you can switch between them as necessary. The d-pad is more accurate on land, the stick more precise underwater. The Wiimote setup is the worst, because the B button is used to run.

And yes, it's more about the graphics than the gameplay. There are lots of trial and error sections in this game.

If you didn't buy it yet, I would advise you to wait until it drops in price, because it's not going to take long until then (if it hasn't dropped already). That's the fate of artsy games. As for your questions:

Its best quality is probably that it isn't a Nintendo game. So if you despise Nintendo, there is a better chance that you will like this game. I honestly can't think of anything that this game does really well, but it isn't terrible either. It just feels average for the most part.

I haven't played the demo, so I can only take a guess that it is a good representation of the first half of the game where the problems aren't as severe. Things can get really hectic in the latter half of the game and annoying when your character pulls off a move you didn't want him to. There's a lot of frustration involved and the plentiful checkpoints and infinite lives serve only as a band-aid for this problem.

The problem with multiplayer is in the level design. By default, you need to forget about 20 % of the levels in this game, because they really are for a single player only. In the remaining levels you need to accept that you most likely won't be able to get everything, because quite a lot of stuff is timebased and the more players there are, the less likely it is that everyone moves at the same pace in those sections.

The main goal of the game is to collect Electoons. Half of them are hidden in the levels, the other half is gathered by collecting a certain number of Lums (these can be timebased) or by doing speedruns. I am not sure on the required numbers of Electoons you need to reach by certain points of the game in order to play the next level, but I think it's possible that in multiplayer you need to go back to previous levels or play some singleplayer.

I bought Rayman Origins Wii version at launch for $30 through Amazon.ca.  It's an excellent two player game (more can join in, but 2 people is great).  It's off beat and whimsical; but if you like platformers, you can't go wrong.  Me and the 2 kids really enjoy it-- and that's coming from a son who is a big COD fan.