I have one, they're pretty freakin epic actually

very impressive for their size.
I've got Mario Kart 8
New super mario bros u
New Super luigi U
super mario 3d world
legend of zelda wind waker hd
and Donkey Kong country, tropical freeze
it's more than just a trumped up Wii, outputs 1080p and uses the on-controller display as a secondary screen very well and very intuitively.
Look for the new Zelda trailer to really see what the thing is capable of. It's all in game footage and literally made me buy a wii U
It's a great little console, the games are genuinely fun, well thought out and are great to play. there's a few gimmicks like the DS led 'blow on controller' stuff but you don't have to use that.
I bought a pro controller and I can happily say it's more comfortable to use than an xbox 360/one or ps3/4 controller, personally I think that anyway.
And yes, it has HDMI out and it carries sound via that as well, or via a standard wii a/v cable if you buy one.