The Zune firmware expected in mid-March is finally out, about two weeks behind schedule. As expected, the upgrade should fix skipping issues experienced by some with content purchased from the Zune Marketplace. It also delivers improved device and software reliability including better device detection and synchronization, and a fix for battery draining issues with the FM tuner.
As expected, no new functionality is included in the update.
Your Zune should automatically detect the update but you can also force the detection through the Zune software.