Let's compare this to iOS 6 where highjacking a phone would take 2 seconds.
Obviously no security method is absolutely fool proof. You are assuming that the high jacker has access to a complex fingerprint mould and is able to actually get a readable fingerprint from the device (this was shown that it's very difficult to get a useable print from a smudge, and almost impossible if the phone has a case).
After 24 hours, the device requires a passcode lock, which would prevent the thief from using a fingerprint mould.
If the customer places a carrier lock/stolen restriction on the device, this would prevent the customer from receiving any text messages.
iOS 7 makes it extremely difficult to steal devices. There are many assumptions here. Of course, there is always room for improvement, but devices using iOS 7 are much safer than iOS 6, where devices could easily get taken over in a matter of seconds. To hack iOS 7, it is an extremely complex process that has many caveats.