Hello,
Yes, it's a serious problem. RME, Motu, Presonus, M-audio, have all reported problems on their forums. RME, who tends to be reasonably thorough (and occasionally arrogant) in their engineering, has done extensive testing to determine many of problems.
If you widen your search on the Apple forums to firewire issues in general, the number of alum iMacs and new MBPs with firewire access problems is extensive. This includes Apple's Firewire Target Disk Mode coupled with the Migration Assistant, such a cool utility when you're purchasing a new computer.
The workarounds on the RME and Motu forums of putting a hard drive in between the computer and interface are only partially effective - many users report this does not work. The other solution of only using the fw800 port, with adaptors as needed, also is not universally effective. And just to confuse it further, some users report everything is fine.
It does not appear to be software related due to extensive testing by RME. They also report that the few Windoze firewire cards that are using the chip have the exact same problems.
Apple, to my knowledge, has not issued any statements on the matter yet. They haven't even issued a "we know, we're looking into it" statement yet, probably because it requires either a firmware update to the Agere chip itself (only from Agere) or a new chip (logic board swap).
I visited my local Apple Store to bring the matter again to their attention. Predictably they were not aware of it, but one audio specialist with a local studio indeed was aware of it, had brought it to the attention and demonstration of some local Logic beta testers, and feels some movement is happening.
And finally, my year-end tax purchases have been massively messed up by the inability to buy new machines.
We'll see what the future brings, but Apple has really dropped the ball on this with some of their most dedicated and long-standing customers, audio folks.
H