Waited a bit too long and didn't manage to snatch a TH-600 at the firesale price of 459/499. Found a few online right now for 499$, but they were all listed on the Fostex official unauthorized vendor page where I assume the warranty wouldn't be recognized.
Picked one up for 540 or so from RazorDogAudio. Looking forward to it after reading a lot of the impressions in this thread. :)
This will be replacing a Denon ADH-600, so I'll post impressions. Not expecting too much of a difference.