Hi guys its my firts post so hello nice to meet you I just want add from myslef that Im quite satisfied with the battery life in my N900.
I bought a week ago from Carphone Warehouse (Vodafone) and after getting it out of the box I charged it fully 3 times for 12 hours. Now I can easily get 24 hours of heavy use.

I go to work @ 9:30 pm, from 10 pm til 2 am listen to music on headphones. 2-2:30 (lunch) i browse net on 3G, some youtube + a few tries in Angry BIrds. then from 3 to 5:45 i listen to music and go home. At home while bathing I have a cigarette + 15 minutes of news via Wifi. Then I go to bed, check for any new repos, and still have 1-2 bars of battery easily. Last wkend I didnt go to work, charged it from empty on saturday morning and it lasted me till monday afternoon. Oh yeah I did some photos sat evening.

Got brightness @ 2, no system sounds, no haptic, always on 2G+Skype on, only @ night i switch for 3G for 30 minutes. Wifi scanning off. No animated widgets on main screen (like fbook or rss). I also try not to wake it up too much when its suspended (like checking time or sth).
Of course all of this dont include texting and calling (around 15 txt/20 mins of talk).

I think its not the problem with the device but how YOu use it. I know it;s a Internet tablet which is meant to stay all time online but hey dont expect miracles from such small battery...

I have idea that can help you - get a desktop charger with spare battery (Ive seen a set of charger + 2 batteries on ebay for around Ł8). That will make Your life easier.

Sorry for length of this post and for my grammar but English is not my native language.