I've spent £437 so far. I hope for speed improvements to the OS, but other than that I'm very happy and have no regrets whatsoever.
My 3 year old nephew loved seeing his Mii created by photo -- I know this is something they've had since 3DS, but he was tickled pink seeing his face transform on TV. Netflix and Lovefilm are both active in the UK now and Lovefilm, in a timely fashion, have gotten rid of the streaming limits/restrictions that used to be in place (I used to only get 4-5hrs a month on my subscription, its now unlimited). I love that even apps like YTube, Netflix and Lovefilm have their own Miiverse communities, I've found myself reading posts about shows I like and discovering silly/stupid youtube videos I didn't know existed. The netflix UI is great, there's an adult mode and a kids mode. In kids mode, there's this kids TV character menu, so my nephew for example can just point at Ben-10 and away he goes.
As for the games...
NintendoLand - brilliant fun, especially with others, but even alone in the case of some minigames. Some can be played off TV (DK Crash Course for example). My 3 year old nephew was able to play the Zelda minigame with me - we kept dying of course, but that gives you an idea of how simple and accessible some of the games can be... and yet some of them are quite tough too. To best the main attractions and top your leaderboards with gold trophies you will fail and fail again. I defy any group not to laugh while playing the Mario Chase, Luigi's Mansion and Animal Crossing minigames.
NSMBU - the single player game is a good standard above recent entries in this series, and modes like challenge mode are a revelation
Sonic & SEGA All Stars Racing - track design and character selection is great, the transforming craft is MK7 - but done a lot better, the online is great, has the kind of battle mode that's been sorely lacking in recent MKs, and it has off TV play.
Mighty Switch Force HD - definitive HD version of the 3DS classic, great fun beating PAR times.
Call of Duty: Black Ops 2 - single player looks beautiful, DF article was very nitpicky in my view, and the multiplayer is flawless fun once you start to stop sucking at it! Taking a guest online and both having independent views (gamepad + TV) is amazing. While online count is still low at the moment, it's definitely the premiere online game for Wii U at the moment if you like shooters, and you can always get a full game.
ZombiU - really striking concept. I can see why the gameplay was polarising but I love it. The sound design is great: your character gets more out of breath and crazed with panic the more you swing your cricket bat... zombie heads dent inwards on impact quite a bit before you're actually able kill one, so it feels satisfyingly violent, and different types of zombies (armoured ex army / police for example) help to keep you on your toes. It's nice to see Zombies can follow you through doors (so you can barricade them), crawl and lay in wait. Aside from scripted scares, you just find yourself nervous and constantly pinging the radar on the gamepad before turning corners. The in-game messages from devs about Survivor leaders and so forth, along with the loss of your loot and a readout of how long you lasted when you die keeps you wanting to survive... and surviving isn't easy.
I also have Puddle, which is just okay. Its a game in the vein of Fluidity / HydroAdventure, but with themed world twists (ie. the liquid changes from water to weed killer, oil etc). It seems quite tough to master later on. I think Trine 2 will be my next game purchase.
The FIFA13 demo has put me off getting the game, despite being initially interested. The gamepad management menu stuff is great, off TV play would be great, but its fundamentally lacking in things that make the other versions good (skill minigames, ultimate team etc). Touching to place a shot sounds great in theory, but it just felt a bit janky to me... nothing to do with the gamepad or the screen, just the way it overlays this giant net over the touchscreen while you're still moving... I can't say I really like it.
I'm looking forward to getting the Rayman Legends demo tonight. If its the same one they had at EuroGamer and PlayExpo, I'm going to play it as much as they'll allow me to before the game launches... it will definitely be one to show off to other people as well in 2 player, its a good laugh.