After hearing about this game I purchased Rayman 1 on my PSP for a few pounds and gave it a play. It was good, but surprisingly, incredibly difficult to complete.
After completing it, I purchased this was the excellent price of 15 pounds from Play.
One month on and it's honestly up there with one of the best game purchases I've ever made (incredible value for money).
The game has fantastic multiplayer capability; playing with friends is really good fun and rewarding (you can revive each other when you die/"pop").
There's a mixture of level types, from boss levels, flight, mini-games, platforming and my personal favourite, the races to catch the chest (find out when you play the game).
It also utilises themes from the first Rayman (as well as others) - it's basically Rayman 1 dragged into 2012.
But, to note, I think to fully appreciate how excellent this game is you must play the original Rayman (the one from Playstation 1).