Pretty good. Smash U's got some great graphics and fun non 3DS modes, but I will say I didn't have as much fun starting to play it as I did when I started to play the 3DS.
I sorta am making my own tier list for my character preferences. The top characters are Captain Falcon and Little Mac. Meta Knight and Zero Suit Samus a bit below them. Toon Link, Ike, Robin, Pikachu, and Lucario are some of my other good ones.