FWIW, I also own two Apple TV's, an Atom-based HDMI-out net top, a Chromecast, and now the Amazon Fire TV. I think the software needs a little work. They need to figure out the pairing issue with the remote. The game controlled needs a serious redesign though. It's painful. Or hopefully they will support third party controllers.
The Plex App on Fire TV is $0.99 and I bought it as well with some of the free Amazon "Coins" that I got from buying the Amazon Controller. I'll update some info when I get the device paired with my Plex Server.