I surely hope that the Ouya will be a success, but I am far less sure that it will be a success. On one hand, making a game for a regular Android device with a touchscreen is a lot different from making a game for a gamepad. ( For example drawing games simply do not work with a gamepad, while football games do not work with a touchscreen/acceleration sensor). Atop of this the hardware seems to be rather low spec, especially the lack of a real GPU seems to be a problem.
On the other hand, with the feature list of the Tegra 3 and a bluetooth keyboard, it would make a really nice streaming client/HTPC. And it is fairly open, which should ensure hackability for stuff like a nice TV interface for HN, home file server and probably even gaming ;)
In conclusion, I have the somehow wired feeling that it could be a rather huge success but not as a gaming device but as the break through for "smart TV." And it is somewhat raising hopes, that the developer specials (at $699 and $leet) are sold out.
 I forgot to add:
The $99 price point is very nice, since this is about the highest amount many people are willing to spend without a good reason. So many casual gamers will probably buy one and figure other uses out later.