Even tough the battery performance improved after the November 13th update, some users notably zune 30/80 GB users were complaining of battery drain when they suspend their zune hard drives by holding down the play/pause button.

Well there is a good news from Cesar the recent 2.3 firmware update puts an end to this problem and also provides some performance improvements like

Improved device recognition

(and)

Improved stability and reliability on sync (both wirelessly and while connected to a PC).

Hopefully after this update we will not hear any more issues related to batteries.