+1.
It's bigger than the jump than from 4 to 4S, but it's still a fairly small evolutionary step compared to what other manufacturers are making at the moment.
Worth an upgrade? Maybe. You'd have to be invested in the apple ecosystem, and at the end of (or coming to the end of) your contract IMHO. That would also mean you'd be upgrading from a 4, not from a 4S (assuming a 24 month contract).