I'm no pomo. Not mo either as far as that goes. But I can recognize the influence of both in my thinking. I'm not sure I have anything to contribute, but here are some hopefully semi-coherent thoughts, rambling and disconnected though they might be...
Post Modernism is not new. The concept has been around for over a hundred years in the areas of art, architecture, etc. Toynbee used the term in the 30's and 40's in a social sense, and most folks credit Charles Jencks, writings in the 70's with popularizing the current use and understanding of the term.
So, we have a philosophy/mind set/paradigm, etc. ad nauseum, ad infinitum, that is at least 30 years old, that tells us it probably won't be able to define itself for a long time (as much as 50 years?), and some of you wonder why we are slow to get in that line?
I hope this doesn't sound cynical, but the vast majority of people who are embracing "Pomo-emergent"-ness couldn't give a rat's about the philosophical underpinnings. They are adapting a style - of dress, worship, etc. For most folks "pomo" means their preacher looks like he was dressed by the boys from "Queer Eye", they can wear flip-flops to church, and there's a Starbucks in the lobby.
"Engaging culture" doesn't have to mean being immersed in culture. John Stott says the message of Jesus was a "counter culture" message. Yes, you earn the right to speak to people through relationships and not by bashing and attacking, but maturing faith should move us away from the world's culture, to a God centered culture. Perhaps what Pomo is trying to do is define what the God centeredness should look like.
I am by nature jaded and sarcastic, and I tend to look with jaundiced eye on the "theoriticians" - Pomo pundits like McLaren, Bell, and some others have been and are pastors, but many have never pastored a church in their lives (Len Sweet?). I will listen a little more to the guy who's done it rather than the guy who's just written about it.
The dialogue needs to continue. In this issue, as in most issues, the ground of truth is found somewhere in the middle of the extremes.