Here's a video of my external firewire disk drives -- one is off ATM and other is executing dd if=/dev/zero of=/dev/sde
I've only built two so far (from cheap CompUSA parts no less), but with one more I could do software RAID 5. And I never need more firewire ports, as drives can be plug into each other in a daisychain.
Right now use mainly for copying entire drives/partitions... easier than cracking open my case every time, anyway. But would be nice to find a firewire NAS like linksys USB one above. If it did RAID too so much the better.
I built the PC too BTW: Celeron 3.06GHz in a VIA chipset mobo. Dual boots XP and FC5. I went with black componentsw and cool blue LEDs this time around.