Finally got one yesterday, with Nintendoland and ZombiU (not played yet) and NSMBU. Thoughts (tl;dr etc):
The box is nice. Two tier slidey inlay thing is genius. Console feels nice. Pad feels nice to hold. Turned it on, was confused when it wouldn't let me log in with my Nintendo account. Discovered I have to make a Nintendo Network account and connect it to my Club Nintendo account which is a different thing. How very retarded. Then I downloaded the update. That took three hours on a 25MB connection. Halfway through it doing that I downloaded a 1.5GB file on my laptop out of idle curiosity to see if it was my connection. That took 8 minutes. Update was eventually done in a shade over three hours.
Finally got in, tried to add a friend. Couldn't see anywhere in Miiverse (there's a way, apparently), then discovered if you press Home to get the Home menu (which isn't the same as the main menu, or "homepage", obviously) there's a friends list where you can add a friend. I've since been told if you do it this way then it uses the traditional fucked up Nintendo method of requiring mutual entry rather than sending a request. If done via Miiverse it does it the sensible way. Right.
Gamepad. It's quite nice, reasonably comfortable. The touchscreen is very unresponsive. Sticks are too far in, d-pad is rubbish. Screen is nicer than I remember though, though a bit oversaturated. Battery life on it is a joke. I charged it for an hour before turning it on, so it had that plus whatever it came out of the box with. It died an hour through downloading the update. Gave it another two hours on charge, and that got me about 80 minutes before it went again. The most annoying thing is not being able to turn the screen off. Playing NSMBU the only thing the screen does is show an exact replica of what's on the TV, it adds nothing. So the battery is being drained at an alarming rate plus I have the very distracting screen in my peripheral vision showing exactly what I'm looking at for no perceivable benefit.
Then I got into the menus. Wii Shop is a bit of a mess, and soooo sloooooow (Rayman demo took 35 minutes to download, it's about 550MB). Also does the silly PS3 thing of requiring downloading and installing separately. At least it has background downloading.
Miiverse appears to be completely mental. I can't make out what's going on half the time, but it's certainly very entertaining. I like it.
So then I played some games.
New Super Mario Bros U
Meh. It's a 2D Mario game. Controls like wading through treacle, levels are predictable and dull. Has its moments where everything clicks and it feels right, but so far (so far just being the first world, granted) they're few and far between.
Rayman Legends demo
Evidently Nintendo don't know how to make a 2D platformer that feels right and shows off their fancy new toy properly. Fortunately it seems Ubisoft do. This is just perfect. Absolutely stunning to look at and listen to, controls like a dream. The gamepad bits feel a little bit tacked on for the sake of it, but they do work, and are surprisingly fun (though the novelty may wear off if they appear a lot throughout the full game). The Castle Rock demo is a work of pure unmatched genius. This is going to be the best 2D game ever, and worth buying a Wii U for alone.