Howdy,
Did a little experiment recently, wanted to see how long my SL-C860 would last when used as purely a portable 'wireless' media player (i.e. streaming audio from a shoutcast station). I found a hack on these boards to stop suspend, threw my wireless card in (Netgear), tuned into cliqhop, put the volume 75% up, turned off the screen, and let it run.
I let it run for about 12 hours, and it said it still had 90% battery left - wow. Would have left it for longer but I use my Z daily :-)
Anybody else care to share what kind of battery life they get out of their Z with various usage? My Z has the best battery life of any PDA I've seen, hands down.