The HDA standard is a huge improvement over the Ac'97 stuff.
I think that firewire and USB stuff is mostly todo with the fact that is the only realy easy
way to improve the audio quality of laptops and such. If your going to do DJ stuff then it's
not practical to carry around a PC tower with a half dozen audio connectors hanging out the
back. And anyways the Macbooks and such are a nice fashion accessory for people who do that
sort of thing.
I still expect that they still cause problems in terms of latency and such.