I found found the best way to get mileage out of the iPhone battery but yet keep up to date is to set the preferences to update mail manually but have contacts and calendars update every hour using the Fetch process. I found the Push method knocked my battery to 50% by mid afternoon with light usage otherwise. I also found that having my Exchange account push information drained it even faster. I hope Apple makes an iPhone update available after today's rumored launch of new iPods.