I'm test user of prototype of N900 with firmware version 41-13. I'm very satisfied of the battery life with moderate use. The best result for me have been 60 hours. I have used all the features and the working days have been normal. In heavy use I haven't seen any difference with earlier firmware versions. If I see a long movie and wlan continuously on then the battery holds 4 to 5 hours. In normal quite heavy use it holds easily 15 hours which is usually enough for me, cos I charge the battery every night anyway.
That was piece of cake. No problem at all to achieve 15 hours with 3G use on whole time. Actually there is 3/4 of battery left. Of course I was in the region where there was good coverage of 3G. If there is poor coverage then the battery drains very fast.