I've had horrible battery life for the first 2 weeks of owning the device, but everything just changed.
I used to get about 10-12 hours max always connected, without much usage.
My battery life has increased considerably **EdIT**
I'm not completely sure as to what did the trick.
**EDIT** I Believe the cause of my battery life increase may have been due to a combination of better reception, and maybe just getting past those first few charge cycles to get the battery to its full capacity.

What I've done before this happened is disabled the touch search widget, and the media player widget.
After doing this I noticed that the 25% battery I had left suddendly seemed to last forever.( Draining about 1-2 % per hour on idle while connected to 2.5G and a wifi connection.)

The next charge after that had the following results:
When in online mode I was always connected to a wifi, except when driving. I had email checking every hour, omweather every 4, and msn haze plugin always on always connected.

~ $ lshal | grep percen;date
battery.charge_level.percentage = 97 (0x61) (int)
Fri Dec 18 01:43:05 GMT+8 2009 removed from charger as soon as turned green.
~ $ lshal | grep percen;date
battery.charge_level.percentage = 92 (0x5c) (int)
Fri Dec 18 02:59:17 GMT+8 2009 after a little browsing before bed
~ $ lshal | grep percen;date
battery.charge_level.percentage = 87 (0x57) (int)
Fri Dec 18 13:23:30 GMT+8 2009 kept n900 in offline mode overnight. Set back to online.
~ $ lshal | grep percen;date
battery.charge_level.percentage = 83 (0x53) (int)
Fri Dec 18 14:28:03 GMT+8 2009 10min chatting, 10 min talk, updated 2 apps. Uninstalled ssh-server.
~ $ lshal | grep percen;date
battery.charge_level.percentage = 68 (0x44) (int)
Fri Dec 18 17:02:00 GMT+8 2009 about 35 mins of talk, a couple of texts.
~ $ lshal | grep percen;date
battery.charge_level.percentage = 65 (0x41) (int)
Fri Dec 18 18:00:18 GMT+8 2009 just checking email
~ $ lshal | grep percen;date
battery.charge_level.percentage = 62 (0x3e) (int)
Fri Dec 18 18:28:28 GMT+8 2009 checking battery and email
~ $ lshal | grep percen;date
battery.charge_level.percentage = 61 (0x3d) (int)
Fri Dec 18 19:55:24 GMT+8 2009 just checking battery.
~ $ lshal | grep percen;date
battery.charge_level.percentage = 60 (0x3c) (int)
Fri Dec 18 20:34:10 GMT+8 2009 just checking battery.
~ $ lshal | grep percen;date
battery.charge_level.percentage = 57 (0x39) (int)
Fri Dec 18 22:05:29 GMT+8 2009 checking battery, messages
~ $ lshal | grep percen;date
battery.charge_level.percentage = 51 (0x33) (int)
Fri Dec 18 22:57:02 GMT+8 2009 15 mins of playing an online game.
~ $ lshal | grep percen;date
battery.charge_level.percentage = 35 (0x23) (int)
Sat Dec 19 02:03:10 GMT+8 2009 listened to just over 3 hours of mp3s on shuffle.
~ $ lshal | grep percen;date
battery.charge_level.percentage = 22 (0x16) (int)
Sat Dec 19 04:42:20 GMT+8 2009 on drive home, listened to 10 mins of music with fm transmitter. Checked messages periodically 45 min drive.

And finally just wrote this whole post and browsed tmo for the past~50 mins, and here is the final battery read.
~ $ lshal | grep percen;date
battery.charge_level.percentage = 13 (0xd) (int)
Sat Dec 19 05:25:36 GMT+8 2009

overal very satisfied with the increase in battery! Not sure what exactly made the difference. I'll test those widgets one by one on my next charges.

I would have to side with you on this one. Mine is lasting over 24 hours on a daily basis now also. I don't use any widgets, and I am only connected to GTalk for a few hours as necessary. Very satisfied!

This just further proves my suspicion that the battery issues on the N900 are caused by bugs in some of the applications..

Well, that's completely normal, just compare the testing the apps go through against the firmware.

Hi dantonic,

I'm the developer of TouchSearch and would be very interested in your results with just it enabled.

I designed it to be extremely light on the battery. In fact, that was my initial priority. It shouldn't use any battery whatsoever when you aren't directly interacting with it.

If you do find that it inhibits battery-life in any way, please file a bug in the maemo.org bugzilla under component TouchSearch and I will get on it right away.

I have media on widget desktop always and use it intensively. My battery lasts forever, full day while on wifi. Screen turned down to 2 blobs, mail every 5 minutes, full wifi, BT on, GTalk status, the works.

It's not the media widget

There must be something very wrong with my apps or something else.

My battey only lasts 6 hours i have wifi on and have talked for 10 minutes during the 6 hours.

Don't forget that different SIM cards consume different amount of power as well.
This can also kill the battery...

What is a touch search widget?

http://maemo.org/downloads/product/Maemo5/touchsearch/

It is just a simple Desktop Widget that allows you to quickly search the web.

It should be available from the Application Manager if you have ever downloaded something from maemo.org Extras.