I have a slight interest in the Ouya given how open it is. With such a setup, there's no telling what some indies will try to do. :P
Absolutely no interest in the Shield though- as it seems to fit a niche that can already be satisfied relatively easily. And is a niche I hardly ever feel a need for.
Oh, and Steam's Piston/Steam Box? Also absolutely no interest. Though of the three, its the most likely to succeed.
Also, Given Ouya's success at Kickstarter, I'd say the Ouya has a better chance than many seem to think- though that 'chance/success' will probably be nothing more than a larger than expected cult following. :P
I don't see Shield doing well at all though- it'll probably be too expensive.