I know a bunch of people who have an iPhone an none manage to make it last a full 24h, most cant get it to last till the afternoon. In fact, even when the thing is charging, it uses more energy then it takes in so it dies in the middle of a call.

Personally I can barely make my 5800 last 18h with email syncing and an a few hours of phone calls and some web browsing/twitter etc.. If the n900 works for 16-18h with my level of use, ill be content.