How do you mean?
I don't actually have one, but I do know it's a little quirky in how it's BC. Like the transfer process to put all your Wii shit on there is kind of hilarious, but if you never owned a Wii it probably wouldn't be too much trouble to fool around with.
The way I understand it is like to play Wii games you basically load up a virtual Wii on the Wii U, and from there you can access any Wii things (which include old Wii virtual console games from the N64, Super Nintendo, or what have you). I'm not entirely sure how it all works though.