Yes, I'm chomping at the bit.
I guy in Australia posted the Firmware on Friday, but it was pulled down while I was considering the risks of using it. (Apparently some cameras that were in for service in the last few weeks got updated and the update ended up on the internet).
In preparation, I tried my EF 2.0X TC-III yesterday on the 500mm using MF. It's useless, at least with my current focus screen. I didn't get critial focus on a single image, even though some looked good to me through the VF.
BTW, there are rave review from Australia, saying it's really fast AF now, taking the 2.0X from useless to faster than the 1.4X with the old firmware. I hope that's true. We'll see soon.