The backwards compatability thing. I keep all my consoles.
Currently I have my Wii, PS2 and Dreamcast set up to the TV in the lounge, whilst the 360 is hooked upto a second VGA monitor on my desk (also in the lounge). I then have an original XBox in the bedroom which is just collecting dust as I think the SCART cable for it has packed in, as well as a second PS2 (both mine are the chunky monkey models). I also have my Gamecube, Saturn and Dreamcast stored away under the stairs. Whilst all of my cartridge based home consoles (SNES, Mega Drive, N64) are all in the loft with my original PlayStation.
So realy, backwards compatability isn't really an issue for me, but it would be more convenient to just run from one system, which is why I have my Wii modded with SNES, N64 and Mega Drive emulators on it.