Updated 'Phone: 24 hours later...

[davester]

According to a site that disassembled one, the iPhone 3g does not have a soldered on battery (though the version 1 does). I can definitely see killing batteries fast with all these cool programs now being used. You just need to make sure you've got charging ability close by or if you're out in the field limit your use of the applications (or carry a portable battery backup pack)
.