The DEFINITIVE Guide to Upgrading to iTunes 7.4.1
I've modded my iPhone with AppTapp while using iTunes 7.3. All of my applications are from there. These instructions, however, should work for any type of modification you've done (Windows and Mac).
Here's what I know to have the most updated software on your iPhone, without any problems. Otherwise, you're stuck using the old versions of everything:
1. RESTORE the phone to its normal state while still in iTunes 7.3. Restore to iPhone Firmware 1.0.2
2. Sync (but don't sync music/photos/videos/heavy files. Waste of time).
3. Upgrade iTunes to 7.4.1
4. Sync again with the new iTunes.
5. Restore again while in 7.4.1. This step might be unnecessary, but I did it, just in case 7.4.1 reinstalls in a different way. Since I didn't play with the iPhone in between, it's an extra 5 minutes of work.
6. Sync for real with all your video/audio/photo files.
7. Use the new versions of AppTapp/INdependence to redo all the mods.
I didn't see these posted here, so I thought I'd share. If anyone has a faster set of instructions that doesn't require losing mods while upgrading iTunes, I'll edit this.
I know these instructions have a lot of extra syncs thrown in there, and possibly one extra restore. Better to play it safe.