I am also experiencing battery drain on my iphone 2G after upgrading to OS 3.0. I literally see the battery percentage dropping in front of my eyes!

I will have it charge at night at 100%, when I wake up in the morning, it will be 80%, get to work 70% and by the time i reach home its 40%. This is with push, bluetooth, wifi, edge all OFF.

I removed my app with push functionality out today. Testing to see if this will help.