In short:
Trine 2 looks incredible.
Nintendo Land is interesting, though we haven't put a lot of time into it. Mario Chase, Luigi's Ghost Mansion, and Yoshi's Fruit Cart have been hit games with our oldest (3.5). Even DKC's Crash Course is fun for him, though he hasn't completed the first level just yet (close).
ZombiU is incredible. Please do not read reviews, try it for yourself. From what I can tell, the majority of "reviewers" on the game did NOT even complete the game before they published their reviews...which is quite sad
Is the game perfect? No. Is it fun? Yes. Especially if you're looking for a survival horror type game.
The TV button/function is awesome. Miiverse is an awesome start, and hopefully can be updated with a few things in the future (a message from developers at the top of each section would be nice). Adding friends is a GREAT improvement over the Wii.
*Edit - some negatives:
1) While my system has only frozen twice (TWICE TOO MANY!), not having a hard reset work on the system is baffling. How a system released and made it out to the general public without the hard reset power button option working, and being forced to unplug it...
2) The YouTube App is worse than the Browser functionality of YouTube...which makes me wonder who made that decision, and if it will be updated.
3) Adding another... The Wii U seems to constantly read the disc when one is in the drive, which hopefully can be patched to solve that. When I'm using Netflix, the Browser, or just browsing Miiverse, it would be great if the system wasn't constantly reading the disc. I think the Wii was able to not read discs when Netflix is being used, so hopefully that is something that can be patched (maybe it already has, but as of now I remove my disc after each play session).
What I have seen so far though, is very promising, and I really do hope they are able to patch/update stuff very easily for/on the system. Again though, if you own a Wii U and have been on the fence for ZombiU...get it. If you go in expecting survival horror, and not FPS action, you should enjoy it. I completed the game last night with more than 20 hours played...and the local multiplayer is a very good option for friends/significant others that might not like FPS/zombie type stuff, because they can use the GamePad and avoid the "gore" aspect by not looking at the TV...really is a great option, and fun.
If you are playing the Wii U on a SD TV (like me), buy Trine 2 on the eShop, and it will show you why you need to upgrade your SD TV to a HD TV.