I have a full Windows 7 PC hooked up to my TV and the embarrassing thing is that the PC is quite bad at playing video. Almost no media players adjust the output's timing to match the video being played which leads to tearing and stuttering when playing video where the frame rate doesn't match the default refresh rate on your monitor. You find yourself either constantly manually tuning refresh rates, or living with broken inferior video output. The only player I've found that handles this issue properly is the one in Plex Home Theater.
Another thing which is rather silly is that it can't act as a Chromecast server, even though it has chrome, a network connection, and a massive cpu and ram. This seems like something that it would be relatively trivial for Google to create, and would make chromecasting much more convenient because I would reduce the number of times I have to switch inputs to get chromecasting to work.
I've gotten x-box 360 controllers and setup emulators. I've done quite a bit of messing around, and in the end I've found the PC to be quite bad at being a TV media device.
I like the idea of Android rebuilt to be controlled from a remote and running my TV, but I don't like the idea of another Amazon based walled garden. Also, I see this as unfortunate competition for SteamOS, which seems like a much more robust and open platform for solving this problem, and I'd like to see it win instead, but the low price of this offering and Amazon's muscle will make that a lot harder now.