I'm cautiously optimistic about the Ouya. I'd love to be able to put Energy Hook on the big screen in my livingroom without having to jump through endless TCR or being tied to XNA.
I think the 'killer app' thing is something of a myth - people say that GTA3 sold the PS2, for example, but at the time I checked the data there were 20 times as many PS2's out there as GTA3's. People go a little crazy and they just buy the shiny new console even if they don't know what they're going to play on it. The amount of funding the Ouya kickstarter has already raised is kind of proof of that - people don't even know what they're going to be playing on this thing and already they're lining up to buy one.
But me, there's some game I want to play that makes me buy a console. With the Xbox 360 it was Chromehounds (and what a disappointment that was - my 360 ended up being a Geometry Wars server for the longest time) ... with the PS2 it was Ico ...
What about you? Is there a game that's currently available on Mac or PC - or coming soon - but not on one of your consoles that would make you say, "Yeah, I'll drop $100 so I can play that on the big screen."