I'm quite pleased with my 80, in a lot of ways, and yes, sound quality is certainly one of them. I've noticed that I prefer the synergy between the Zune 80 and the KSC75s, and to that end I've ordered a pair of PortaPros to try out. We'll see how it goes.
I'm surprised that no one here has commented on the trade-off for the lack of equalization in the new Zunes. I'm not sure if anyone here knows this, but the Zune designers specifically omitted the equalization chip to both aid battery life and, much more importantly, clear up the signal path. It seems to me that this would be an amazing find for people here; isn't that similar to why so many people get iMods?