https://www.youtube.com/watch?v=d4X9k7oYN5s You get a quick glimpse at it in this video ... I guess it's an old FW. EDIT: Another one, but probably more advanced https://www.youtube.com/watch?v=Cety-fCq6pw Maybe the first video showed the in-game XMB that everyone wanted back in the day, so that's why it's maybe only showing 4 icons ?
The whole limited menu thing looks like it's based on the main menu, I remember there being an IGN video floating around (called "Direct feed" + something), with them showing a PS3 Dev kit menu with an old firmware. Also the menu sounds were quite similar to the PSP firmwares It did have an In-Game XMB as well. http://www.joystiq.com/2006/08/22/watch-a-video-of-the-ps3-interface-pretend-its-you/
