The guys at Zune Info.com found this yesterday. I've had this on my device for a while so can't vouch for speed improvements but you may want to check it out. Be sure to click Check for Updates with your Zune connected to get this.
Link to » Zune Firmware Update - 1.2 - Zune Info
And apparently there's an update for the desktop software coming later today as well.
sweet - thanks for the heads up Barry!
It's on microsoftupdate now. And it has native Vista support. No real hint at what's new though.