Hello lordedward,
I think the reason people are giving firewire the "big thumbs down" is because firewire uses a buffer that creates a realtime delay between when you play your midi/audio into the computer and when you hear the playback through the DtoA or monitors. I know because I bought a PreSonus firestudio before I knew anything. I read an amazingly optimistic review from tape op about it and I was sold on it.

Ok, so I would say that I have no regrets now that I am comfortable with how my setup works and have so little delay that it does not bother me anymore. So, a big drawback of the recording buffer is that you should use the fastest rate available to record. The firestudio uses a 96k rate and this reduces the delay from 48k by double. In other words its half the delay of when you sing to when you hear your voice in headphones. Only drawback is the increased processor use and drive space needed. Also, your plugins are working harder too. However, I do really like the sound of 24-96k increased fidelity now!
So, if I would have known more before I made the plunge I am not sure what I would have done. I had been running an old 8100 ppc mac for eons (1997-2006) and I had not wanted to update my computer until I saw a significant jump in power. I guess sometimes you just make the jump to a new system and adjust accordingly, no matter how long it takes to adjust!

http://www.myspace.com/bretnorman

Best wishes to your audio dream sound,
jammster