Summary: I've had these for a considerable amount of time on a mac pro. The idea of everything running through a single firewire cable was what was appealing for me, as well as the looks. Unfortunately this system is flawed- if the music is too loud it shorts out the firewire bus and the speakers go crazy. The firewire cable is too short for a tower. It also is pretty poor quality audio for the price, better than built in speakers but not much.
Summary: OK so, people are right about the hiss. These guys hiss noticeably. Why do they his? It's completely digital. Theres no reason for them to hiss, I find that odd. Also, they don't have that much bass. I know, they're only bus powered but still, firewire has a lot more juice than USB so I was expecting a little more umph. They sound quality is nice besides that though. However like someone else said, they are very loud.
Summary: The sound is great until they suddenly die. Have owned 2 sets of these. The first one died in less time than the second set. Will not buy ever again. Way too expensive for such a short life span. Now I'm even afraid of getting the USB model because of this bad experience with LaCie hardware.