Google will put out a far than better product than Ouya for about the same price.
Imagine taking your phone and touching the top of the device to auto sync, then using the phone to start some game. Then put it down and pick up a bluetooth sync'd dual analog controller to play the game.
Phone still works as phone as the game is actually running on device, phone sync just told device what account and then what content to play.
Imagine a 2nd person comes in and syncs their phone because you both want to play the latest FIFA on the Play store, but its his copy, well now system is sync'd to both your accounts, he starts game and picks up 2nd controller. (keep in mind Google lets you proclaim up to 10 devices per your android account and a single device can be shared infinitely)
OR later you're wanting some music for a party. You, your wife, a few friends all sync their phones by just tapping to device (NFC and wifidirect). You all individually from your phones create a dynamic playlist from anywhere in your house.
Basically, Google's device will likely be the perfect android media streaming device that is truly unique to you as its base around your temporary sync to the device from your phone or tablet. It automatically can access your Google Play media of any type and stream to TV (or neflix, browser, hulu, youtube, books, and so on).
Google the "Google Q" device. It almost did all of this (sans games) but was made in USA and way too expensive as well as no GoogleTV experience. Just music and videos for $350. But all the sync'ing and sharing was there.
Now add in the full GoogleTV experience (pretty much all the features XBone is touting), real games controller support and likely large increase on high quality console games, all this instant sync/sharing features loosely defined above and for a price of $100 to $150. Controllers like $30 (because Google doesn't add massive margins on anything... see Nexus phones launch and $300 when others are at $600 and better quality too).
This can be huge if Google doesn't fuck it up.