Been playing it for the last week. I think the game gets better and better as it goes on, there's neat diversity in the levels. I think my favorite level so far is the "Hall of Heroes". It's capped off with a pretty funny nod to Kickstarter.
@Abdooooo I have the 3DS version since I don't have a Wii U, it seems perfectly suited to portable play because the levels aren't extremely long and the checkpoint system is good. Plus the 3-D effect is pretty cool, you get some nice depth with the parallax scrolling.
That said I'll probably buy it again on Wii U some day because I bet it's awesome on the TV or Gamepad too!