Initially the n900 battery life was horrid. However, after about a week of use the battery life tripled. Why? I have no idea. Anyhow, I now regularly get 2 full days of usage before I have to charge.

8am: I pull the n900 off of the charger before I head out the door.
Take a few of calls throughout the day.
Calendar reminders throughout the day.
e-mail and web surfing during my lunch break (about 30 mins of 3G usage)
When I get home at night, I only see a sliver off of the battery indicator which probably means about 80 percent (Purely just a guess).

My setup is a N900 with T-Mobile using three desktops. The only refreshing widget I have on is the calendar. The rest are all contacts and application launchers. I turned off all GPS and network positioning; if I need it then I can manually turn it on (the city where I work has a mobile device ban anyhow). I also leave off WIFI scanning. If I am near a AP that the n900 knows of it will automatically connect to it if I open the browser anyhow, so I don't see the point of leaving that on. Oh, and I turn off all data connections after I use them. Keeping to that strategy, I get significantly better battery life than most other smartphones I have owned.

Anyhow, I hope this helps some of y'all out there.