As you may or may not know, I am a HUGE iPhone fan. Needless to say, after I installed the new 3G software, I was extremely disappointed with the battery life. The phone seemed to die after a round trip to the local CircleK for my big gulp! I exhausted the internet discussion forums, as well as 3 trips to the "Genius" Bar at the local Mac store, before finally cracking the code on my own. Here's what I found out: My Exchange Server Email was sending ghost emails, to my phone, every 3 seconds...thereby draining the battery life. To resolve the issue, I adjusted the following: Within the Settings/Email, Contacts, Calendars: select, Fetch New Data and slide PUSH to the OFF position. Then, select an appropriate FETCH time (mine is set to Every 30 Minutes). Keep in mind Email still automatically downloads whenever it's opened or checked.
Voila! I'm back up to a reasonable battery life of @14 -18 hours!