here is a pic of my battery graph with light usage.

from 3pm to 12am I was at work with wifi always on, always connected, very light surfing and texting through GV plugin. email every 15, omweather every 4. gsm OFF.

at 2:30 am I switched to offline mode and went to sleep.

at 10am I turned back to online and turned on gsm, checked voicemail, then started using the N900 heavily transferring files etc.

the main drain culprits are usually gps,3G data,2G data.... wifi is not a big drain.