I already got the Ouya, its game library is not very impressive (but there are a few good ones).
However the strong points of the system should not be understated, I do not see it as a replacement to any major console (be it the Dreamcast, PS2, og xbox, gamecube, ps3, xb360, ps4, wii U)
However, a real port of xbmc and the emulators make it a must have in my view (it should probably be called the real next gen according to some, simply because the media streaming capabilities are really there and the graphics are really bad!)
The controller is not as bad as some make it out to be, but it's certainly not up to par with the PS3/4/xb360...
but it's only 100$ or so, so you should be willing to pardon a lot to it!
oh, it's always online, as in: if you loose connectivity 1 second your purchased content can't be used... much worse than MS was offering in that regard, so I DO NOT spend on their store, no matter what (the free stuff works even offline, in that sense it's better than the xb1 was supposed to be, until the reversals).