I think that an always on data connection over 3G is the main problem regarding short battery life. When i sign in on one or more of the im networks or let it check my emails regularly throughout the day my battery won't last a day. It makes for example a big difference if you check your mail in certain intervals or use push mail. Using push mail my battery holds up much longer.

I really hope this can be improved. htc dream or hero, for example, don´t have this problem. They sync google stuff and widgets whole they long without losing to much power.