apt-get update
apt-get upgrade

with 32M in rootfs now juste 27M left , 4 or five updates and it's the end of my rootfs

For battery life problems i can use my N900 for 48 hours with wifi always connect at home and 3G via orange (france) all the day (emails....)
(i shutdown my N900 at night beetween 23:00 to 7:00)

before i had only 5 hour of battery life !

The only thnig i change is to not use "Disponibilité" (in french... i have a french n900 so ...) in 3G dont use yahoo,msn........ only with wifi
and battery life is now like other phones (but better than iphone)

so dont use instant messengers with 3G/GSM and your battery smile to you !