I should be more specific, and now that I've been working with the unit for a couple weeks, I can be -- on the D/A side, I hear more detail and separation of sound, with better stereo placement - makes good mixes sound better and bad mixes sound worse. Reminds me of when I went from computer speakers to the low end monitors that I use now. The change is even more noticeable for bad mixes using a decent pair of headphones.
On the input side, there was an edgy high-mid hype that's gone, and it seems like the pres are more demanding with regard to mic placement (this could be the improvement to the D/A side, but it does seem to be more of an issue for new tracks). I'm finding that I have be more precise with X-Y configurations, for instance. Currently, this is slowing me down, because I'm having to learn more about placement, but ultimately I believe it'll lead to better work product once I get the hang of it.
I do realize that, along with the improvements to the unit, I have to account for a) improvements to my own ear/brain that are occurring as they do for noobs who work at it, and b) my imagination, but I really do notice a big difference. Perhaps the context of the rest of my system (monitors, room, brain, cables, etc.) brings it out as well.