....is not a feature of iOS 7, it is a hardware feature of the 5S.
I have the 4GS. I've heard horror stories. Anyone having problems?
Is the fingerprint scanner mandatory?
If I upgrade I plan to back it up to iTunes. Can I restore it and have everything I had before the update? I have very little on the phone except a few apps and phone contacts. I have 10 Gig space available so I shouldn't have to delete anything for the update.