I have one, and it's perfect! Especially after I bought a 25$ airmouse with minikeyboard on the back as a 'remote control' my silent mini-PC completely replaced every other TV input I had. Metro UI is perfect, and there are just so many apps to spend an evening with.
My cable company has a perfect TV app, much better and faster then its stupid slow box, also much better than any stupid slow 'smart' TV app. We have HBO, Netflix, a number of rent-a-movie apps and of course websites! So many websites are perfectly suitable for a TV use case. Check the weather and traffic in the morning, etc. etc.
In weekends I have the F1 standings app on the TV and the Cable app with the live race stream on the beamer. There are a lot of other motorsport streams available online, and the same probably goes for a number of other sports, I wouldn't know
Watching Twitch streams on TV also works surprisingly well. Gaming is something I was suprised to see perfectly possible with Steam streaming from my game PC in the other room. Threw in a couple of Xbox controllers and a receiver and I did not even need an XBox anymore.
Seriously, so many apps, so many usecases
I seriously wonder why Microsoft did not see the potential for this utterly AppleTV-crushing opportunity. It's just so versatile and so pointerfriendly. Get one yourself NOW!