I just upgraded my iPhone 3G to the new OS today. I must admit that the new features (especially the ability to group apps together) is quite nice. I wish I could take advantage of the backgrounds but that doesn’t work for a 3G phone.
The biggest complaint on the entire process is that it took FOREVER to do the upgrade. It took over 4 hours to do the backups, reflash the ROMs, and then re-sync the apps, movies and songs back to my phone
My biggest advice to anyone that is going to do this upgrade soon – take your time. Plug it in, get it started, and then go do something else for several hours.