I'am using mythbackend on a Gentoo-based server in the current version 0.20 with a PVR-500. Have currently 3 frontends running, one in the living room (Gentoo-based MSI MEGA Barebone) and two on desktop PC's (one gentoo-based AMD64 and a Kubuntu AMD64 machine)
Since I live in Germany i have to wait until March before i get my Playstation 3, and then I will try to get Mythfrontend running on it so in order to replace the barebone in the living room. If I get Mythfrontend running fine on the PS3 i will probably post some kind of Howto in the Wiki or contribute content to existing pages.
Update: I started with my first experiments. Im documenting all info i gather here: MythTV on Playstation 3