it probably would not be that bad...in my office, we have a dedicated iMac that works as a file server. We all log into it, open our drawings, work on them, save 5-10 times an hour, and that is a single harddrive, over a network none the less. It handled it just fine, so if you COULD get a single FW drive to mount on 2 macs, it would work very well I think. I do not think it is possible though.
anyone know more about IP over firewire? which is what you'd have to do to get that to happen though.