Although I am not home to specifically verify all channels in DD5.1, PQ is on par with most other HD channels. Local news broadcasts seem very clear and network shows are as expected. This is saying something also as I am fairly picky. (I don't even browse the SD channels on my guide..)
I do have a full 7.1 system and the one little thing I have experienced so far is that in the most recent episode of Revolution, I heard a pretty significant 'leveling' of sounds during action at one point.. meaning instead of it getting louder, everything was actually quieter.
I should be able to report more in the coming week as I record and watch some network shows.