I have a Wii U. It's pretty good.
The tablet feels a lot like a SNES controller. It LOOKS big but it's barely over a pound. Super light and comfortable despite its size.
It's really clever.
I only really play black ops 2 right now but im glad i got it on the wii u instead of ps3.
The game can stream to both the tablet and the tv so, if I want to quietly play, I can plug in my headphones and turn off the TV and have, arguably, a better experience than the big tv.
The graphics are a lot better on the Wii U. It runs natively at 720 then gets hardware upscaled to 1080p whereas the console versions run something like 520ish and upscale from there. Plus it has a bit more AA.
One really annoying thing is the inability to access the wii menu from the multiplayer. It just cock blocks you out until you log out and go into campaign mode.