new iPhone 3G, go with the 8 or 16G? I've got three iPods now, so I wouldn't be needing to put loads of music on it. But, with all of those apps, and my complete disergard to ever erase any text or e-mails, can it be filled wthout trying real hard?
Battery life on the 3G is bad. The 2.1 firmware release notes claim that this is improved for most users, but I haven't had it installed long enough to see if there is any difference.
I would suggest the 16GB for one of the reasons you mentioned: the apps. Over time you may find that you are installing a lot of these and the space will come in handy. Podcasts and videos will eat a lot of space as well, if you have those.
Speaking of which, I installed an app yesterday called Air Sharing. It's a free (for now) app that lets you connect to the device over wi-fi and create folders for storing files. It will mount as a shared volume that you can navigate from your Mac or PC. Pretty handy. I like it so far.
The battery life is much worse on the 3g compared to first gen. I only have first gen, but I know several that upgraded. It would make sense because its the same battery and the 3G radio gobbles way more juice than the standard one.
If you're a heavy user you wont be able to go whole day w/o recharging it.