So I got a Wii U not too long ago and have been messing around with that for a while. I thought I would post my thoughts about various aspects of the system.
The system itself looks a lot like the original Wii, but larger. In fact, the size is almost awkward looking, as if this is the prototype of the original Wii before they shrunk it for release. Although it's not an ugly system by any means. It's much smaller than its current competitors, the 360 and PS3, by a large margin. It should fit into any entertainment center. My favorite part of the appearance is the more rounded look compared to the Wii and its more jagged edges.
I have the black version, but both versions are covered in a glossy finish that looks nice but will attract dust and fingerprints like a magnet. The system features the same sort of slot loading disc drive as the Wii, which is a nice touch in my opinion. I think these types of disc drives seem a lot more... modern, compared to traditional tray loading versions.
The system has full compatibility with Wii games, controllers and accessories but unfortunately lacks ports for Gamecube controllers and memory cards leaving it unable to play Gamecube games. Playing Wii games is done via the Wii Menu which basically reboots the system into a sort of "Wii mode" that runs the OS of the original Wii. When in "Wii mode" you're unable to use any Wii U accessories or controllers such as the Wii U Pro Controller or the tablet-style gamepad.
As far as horsepower goes, it's good. Nintendo doesn't think that specs for consoles are very important and I agree. If you want a stat-box with 100 gigga-wombats and 18 gajillion terranoodles of RAM you should build a PC. I have a PC just for that purpose. Anyone arguing about hardware specs on a console are missing the point. Consoles are first and foremost about games. It is a capable system and in the right hands I can see some really amazing looking games coming out on it. If you have doubts about its abilities, here's a demo they did at E3 2011 to show off what kind of things the system is capable of on the graphics front. It's running in real time on the system in 1080p.
The interface seems more modern than the Wii interface, which I found good but kind of goofy. The channel system on the Wii worked well but some of the channels didn't make much sense to me, like the "everybody votes" channel which seemed like a novelty for small children. The Wii U interface is separated into two parts. The gamepad displays a DS-like arrangement of icons for system features and games. The TV displays the front page of Miiverse, which is a sort of social network that Nintendo has developed for Wii U. People can post screenshots, drawings and text regarding various games and even things like Netflix. Here's a pretty good video.
As far as games, I only have a few right now. The game that comes with the system, Nintendo Land, along with New Super Mario Bros 2, ZombiU and Ninja Gaiden Black Razor's Edge. All very good games and I would highly recommend them. I don't think any of them really show off what the system is capable of yet, although Mario Bros is a very beautiful game and Ninja Gaiden looks great as it always does. Going back to the system itself, one of the things that impresses me about the Wii U is that a lot of the games are available digitally through the Wii U itself. The Wii U supports external HDD's up to 2TB in size to store games and game content on, along with SD cards like the original system. I didn't expect Nintendo to embrace digital distribution to this degree, but I'm pleasantly surprised by it.
Okay, back to the games. The system has a decent selection of games out now, including the ones I listed, which, again, are all awesome. This system is in somewhat of a temporary drought right now with not much in the way of releases until March. On the horizon, Nintendo fans have a lot to look forward to with Wii U. Games such as Bayonetta 2 (which is a Wii U exclusive) Lego City, the usual suspects such as Zelda, Smash Bros, Mario, etc and many more from Nintendo and other third parties not yet announced. Nintendo has already confirmed a new 3D Mario and Mario Kart to be at E3 and in playable form with a new Zelda (along with an HD remake of Wind Waker) coming in the not-too-distant future. There's a lot more that will be undoubtedly announced at E3 so watch for that.
The main attraction of Wii U is the gamepad. It features... almost everything, really. It has the standard ABXY start/select button layout along with L and R bumpers and ZL and ZR triggers on the back with two (clickable) analog sticks and a Dpad. It also has stereo speakers, a mic, a headphone jack, a front facing camera, a built in sensor bar, a gyroscope, an accelerometer, a magnetometer, an NFC (near field communication) reader, a volume slider, a stylus, a power button and a "TV" button which allows you to use the gamepad as a remote for your TV via the IR emitter. Oh, and it has a 16:9 ratio touch screen on the front. Some games use it extensively and very well, such as ZombiU. Other games like New Mario Bros U use it mostly as a replacement for the TV, should the need arise. This allows you to play the game entirely on the gamepad while the TV is free to be used for anything else. Only some games support this and I haven't personally had a use for it, but it's a really cool feature.
The gamepad is light and comfortable, although really large for a controller. The battery life is about 3 - 4 hours, which isn't that great. The good news is that Nyko (along with others soon, I would imagine) will be releasing batteries far better that you can simply swap out yourself to get more life out of the thing. I'll be doing that ASAP. The gamepad offers a ton of possibilities for games and should give us a lot of interesting experiences only available on this system. Don't forget that the Wii U also supports your standard Wii remotes (with or without Wii Motion Plus) and Nunchucks along with or instead of the gamepad.
I've written too much already so I think that's probably enough from me on this subject for now. Overall, I'm enjoying the system and looking forward to what the future holds for it. If you're a fan of Nintendo, I'd highly recommend getting a Wii U. If you aren't a big Nintendo fan or are on the fence about the system for any reason, keep an eye on it. It might surprise you.