Gah, quite sorry to hear the battery on that 20gb Zen Micro is only 11 hrs. What the hell happened, weren't the Zen Touch/Micros clocking in at 24hour battery lifes?
I would've considered replacing my iRiver H140 with it if the battery wasn't so poo.
But I'm still happy with my H140. So I put it forth as a recommendation.
40gb, 16hr battery life (there's higher capacity aftermarkets available now which are easy to install), MP3, WAV, WMA, OGG playback, FM radio, Line in, line out, Optical in, optical out. Built in Mic (useful for dictaphone style use, lectures etc.), recognised as external HDD with no drivers in Windows XP/2000, drag and drop.
No gapless at the moment due to iRiver releasing pretty shitty firmware. But Rockbox group are currently coding their own firmware which is offering a load of cool features including proper gapless playback, and even features a GameBoy Emulator!
Check out
Mistic River's forums for really good iRiver community and information on Rockbox's upcoming firmware.