Firewire became almost only pro audio solution for a set of reasons. Now anything with firewire is more expensive then usb version
(audio mixers, portable harddrives) Not that Firewire would be worse then usb 2 for an mp3 player.
In fact Firewire 2 with doubled transfer rate of regular firewire would be indeed, erm... faster?
I guess everyone is after wireless connection even if this is at the cost of transfer rate. Only today I saw a review of a new Archos player with wireless. ..
This is probobly the direction they invest their R&D money, apples and the likes, they seem to have ditched firewire altogether - except for pro stuff sold at premium prices...