We've already had a few reports of some problems with the latest Zunes (and the latest firmware), and it now looks like there's another issue brewing, with a number of users complaining of battery problems with Zune 30s and 80s loaded with the most recent firmware. Apparently, the Zunes have the unfortunate tendency to rapidly drain their batteries, even when the player is not in use. Judging from the discussion on the Zune.net message boards, that particular issue seems to be due to some unknown difficulty the Zune has with entering hibernate mode which it, seemingly, doesn't do at all (at least among those who've reported problems). Those finding themselves plagued by similar battery issues can apparently "fix" the problem by holding back and down on the d-pad to shut the Zune off completely when its not in use, although we're guessing few will be completely satisfied until Microsoft chimes in on the matter.
Update: Zune-Online.com has gotten word of another fix that appears to solve the issue, at least on the Zune 30. To get things started, you'll have to first drain the Zune until you get the exclamation point, and then fully charge it again (leaving it overnight, if necessary). After that's done, you then reset the Zune by pressing up and back simultaneously, which should set things back on track . Not a perfect solution, obviously, but it seems to be the best option for now.