FWIW, Moonfin and Infuse both work flawlessly on an AppleTV.

I also remember Google TV working fine, but it seemed like ads got added to another part of the UI every month so I got sick of it.

Roku only supports text subtitles, so if you have picture subtitles (like a DVD or bluray), then you'll need to burn them in if you want to play on Roku.

SenPlayer is also very good on ATV.