My biggest impression was that this year it feels like I didn't learn as much. I think that's partly because I've been in position to learn a LOT in the past two years since my last PREC...so there's less to surprise me with...and MOSTLY due to the fact that this year just has more questions than answers.
The 80000000 lb gorilla at this year's conf is the -10dB HD injection issue. Increasing our HD injection by 10dB solves a LOT of the current technical problems plaguing IBOC. But it also drastically complicates our transmission faciities, and there's many, MANY very serious questions about both adjacent channel interference and even self-interference digital-to-analog.
All these questions have no answers yet but they affect everything so much that a lot has been put on hold in the meantime.
I guess it's not that I didn't learn as much...it's that I learned a lot about how little we know at this point.
In other news...David's book (www.ibocbook.com) got some nice plugs during some sessions. Sweet.