The Wii U is my main entertainment device and it's also my universal remote. There isn't a day when the console isn't turned on, even if it isn't being used to play video games. Netflix is a good app, but I'm hoping it gets updated to the updated interface that features profiles and such; It so much better looking. Beyond that, it works wonderfully, however navigation stutters here and there, but it's truly no big deal. The touch screen really does make a difference. Hulu performs just as well, but without the occasionally jitters that come with Netflix. I haven't had problems with it since an update some time ago. Amazon Instant Video is nice, too. It's not as smooth as Hulu, but it's still good. Again, the touchscreen helps out a lot. I'm not a fan of the UI, though. It seems overly complicated. That's not a Nintendo thing, though. I use that app for mostly renting movies.
YouTube recently had an update sent out for its app, but I haven't had much time with that. I use the internet browser for that, and it's fantastic. I find myself constantly using the Wii U's internet browser over my laptop or desktop computer. It's just convenient. It would be nice, however, if I could browse the 'net while watching Netflix or something.
We use TVii mostly too keep track of our favorite shows and for its TV guide. We dropped our satellite provider months before the console came out, in favor of a streaming lifestyle, but we do watch the occasional local channel. TVii has an on-screen TV guide that's very handy, and if you have a DVR, it'll interact with that, so you can set your recordings and all that. It'll also switch inputs and open up apps if I need it to. For instance, if I'm using TVii and see that Vampire Diaries is about to start on a local station, I can click the episode icon and it'll show me where I can watch it; TV, Netflix, Amazon or Hulu. Those options change depending on the show. So, this episode of Vampire Diaries is only available through a local station because it's the first airing, so I'll click the button and it'll switch inputs and direct my TV to the proper channel. It's really nice.
That being said, TVii still does need some work. They've tweaked a bit since launch, but it's not the smoothest of interfaces. In fact, it resembles the Amazon Instant UI, which, as I mentioned, I do not like.
EDIT: I forgot to mention that the lack of blu-ray support is a bit off putting, but I can manage switching inputs. Also, I would like if they opened up the USB ports on the console so that movies could be streamed from a hard drive.