Maybe you know this if you scour the DUC like me...but here are some very facts about the PTHD straight from Digi techs:

1) The 192 has better clocking than any outboard master clock. (less jitter than Aardsync, Rosendahl, whatever..)

2) The dither in the dither mixer has been improved

3) Truncation errors on the master bus have been improved! Wow!

4) Headroom increased to 48dB! Double wow!

I think the last two are pretty significant that i haven't heard much about. .can't wait to hear!