I was kinda Lukewarm toward NSMBWU because I hadn't played the Wii installment (fearing it just wouldn't be much fun after the disappointing NSMB DS, and it was strictly a multiplayer game), and here on vacation with family, and FINALLY playing it, I'm seeing how wrong I was. Not only is it fun with Multiplayer but I'm itching to eventually do a single player run.
The one thing I hate though, coming from Rayman Origins, is how easy it is to impede each other and how you have to be REALLY careful not to trip each other up. Yeah I know it's fun to to mess people up, but for ones actually trying to beat the game, it can be an exercise in frustration (especially for my little brother, he can be a little testy).
But in any case, NOW, I'm really hyped for the Wii U title!