Read the Apple forums for the 5 minutes it takes to see all the problems people are having with the adapter using audio interfaces. Add the fact the only bus-powered external drives are USB 3.0 and then factor in the cost of compromising by using USB 3.0 or USB 3.0 to port multiplier adapters with multi-drive eSATA enclosures and you're still spending significant money compensating for leaving off 1 standard, widely used port and the missing internal expansion while still having issues with numerous audio interfaces.
I agree, also doing audio work, I wish they added some firewire 800 ports.
It's going to be crazy expensive to move to Thunderbolt native solution.
But audio industry is moving slowly to Thunderbolt. Universal Audio, Apogee and Avid already have thunderbolt interface solutions, and i expect other Audio manufactures to follow suit by Winter NAMM.
For storage, thunderbolt native solutions are still rare and expensive, but wicked fast. I hope more prosumer solutions come soon. USB 3.0 is a valid solution in the interim, however. Just pop your old HDD drives out of your firewire enclsoure into some cheap USB 3.0 enclosures for now until more thunderbolt options become available.
A tough transition, but doable.