I personally hope that firewire bites the dust. I have had nothing but problems with it ever since it first started showing up on macs. I haven't used any FW800 devices yet, so no opinion there.
FW400 uses cheap cables and a bad connector design. A bad cable can cause the data and power wires to short, which usually ruins the audio interface and the computer's firewire port(generally a non-replaceable portion of the logic board).
This article has some good information on this subject:
WiebeTech Micro Storage Solutions -White Papers
Ever since Leopard, it seems like most of the firewire audio interface manufacturers are having nothing but problems getting drivers to work reliably, despite their claims that they are manufacturing their devices to apple's specs.
I think that apple should ship all of their computers with an expresscard slot instead of firewire ports. I really regret buying a 24" imac, I have had nothing but problems trying to get a reliable audio interface to work with it, my only options are FW or USB.