The web browser is the only really wicked thing I've seen WRT battery; RSS reader was supposed to be bad too, but I never used it. The browser sometimes starts cranking away madly (I'm not sure of any site-specific correlation, because once it starts, it doesn't stop no matter what site you go to...) and though it doesn't have much effect on performance of other apps, it does drain the battery. I just close the browser when I'm untethered for any length of time, and I get standby times like they should be.

BTW, in Diablo (public release expected around month's end, more or less) the softpoweroff is working again, it seems. You can set up that on long or double-tap of powerswitch and get reasonably decent behavior; never had trouble with it dying in a few hours.