ProLogicIIz Explained a bit.
Dolby ProLogicIIz matrixes info off of the sound track and sends it to a set of "High" channels. It's really nothing more than an extension (height-wise) of your front L/R channels.
THX already has a spec. out for these pressence/height speakers (whatever you wanna call them), however it hasn't been implemented in anything for the consumer...yet.
Audyssey and THX already have a consumer product in the works (almost done according to Audyssey) that does a similar process like the Yamaha pressence speakers and the D-PLIIz. I had the chance to actually hear a beta demo. at CES this January. Pretty impressive stuff. They played a 7.1 track of a live Blu-Ray Jazz performance, and then they kicked in their 10.2 speaker spec. with the High L/R channels, and it really deepened the soundstage and added the affect of a live Jazz hall better than I've ever heard it (other than live). The extra channels add a sense of realism that I just haven't heard in a separate configuration (a system without "pressence" speakers).
Now while pretty much none of that pertains to Dolby PLIIz, and since no one has heard it yet, I can just guess that it will have a similar affect on the front sound stage.
Good job and happy listening to anyone that implements the extra channels into their home theater system. My hats off to your for pushing our digital audio envelope.