There's not much to say here, because according to Zune Insider there are no new features added to the Zune desktop software, just more "performance enhancements around set-up, sync and as always general reliability". I was really hoping we'd see some improvements in the way of meta-data handling (their current system is what's causing some people problems with albums not being read properly).
So basically, if you fire up the Zune desktop software today, you should be notified about the new 2.3 update. Myself, I'd report first-hand on any changed, but my Vista-based machine that's running the Zune software is completely trashed from a software perspective - I updated the system BIOS and nVIDIA nFORCE drivers and now Vista won't boot. <sigh>