Hi again Simon, I saw your PM and was just about to add to your thread, but it looks like you've already done much of the typing I was about to! As you said, the PS3 has excellent media server capabilities. You can download free media server software onto your PC, and put any media files you wish into the folder. My brother said he used TVersity back when the PS3 was first updated with media server capabilities, although he said he isn't sure whether that's still the best program or whether it's still free. Here's one thing I'm not sure about though. If you buy or rent a protected movie through itunes on your pc, and save it to the media server folder, I don't know whether the PS3 can play the protected file through the server.
Oh, and my brother said that whole backwards game compatibility issue I talked about was only for PS2 games. The new PS3's can still play PS1 games like point blank, although the gun won't work on the lcd or plasma as you said. As an fyi/trivia, he said there's a flashback sequence in Metal Gear 4 game for PS3, where you play a part of the original Metal Gear PS1 game. In actuality it's the real PS1 game that you're playing in that moment (not a PS3 recreation), and it uses the PS1 capability of the system.
Austin