Much, much better than iPhone 4S on iOS7
The battery life on my 4S was marginal when I upgraded to iOS6 (and stayed that way through iOS6.3), and was probably even worse on iOS7. I even went to the Apple Store to have them check the battery under Apple Care+, and they claimed the battery was fine.
The battery life of the 5S is significantly better. I generally leave BT and WiFi on all the time, turn off background updating, and try to keep apps with location services on to a minimum. I also keep LTE off as the AT&T faux-4G speeds are plenty fast for what I need when off WiFi (and I suspect that's a huge part of the power savings, but the 4S didn't have LTE.) Whereas I sometimes couldn't get through the morning without feeling the need to recharge the 4S (have cords at home, at the office and in the car, plus an external battery pack for emergencies), that's not the case with the 5S. I'm not sure it's an all-day battery with heavy usage, but it's a lot better than the 4S (and the 5, from what I gather), and I've been pleasantly surprised. I can't quantify the additional run-time, but I know it's better just by how less frequently I am charging.
Ironically, I bought a Mophie Juice Pack Plus case for the 5S. It's quite nice without being too bulkly, and the added weight is not too bad given that the 5S feels quite a bit lighter than the 4S. But now I can use it mainly for trips/weekends when I'll be away from an outlet, and that's all good.
I'm glad I waited for the 5S. Will wait for the 6S (or equivalent two years from now) before another upgrade. For the form factor/size, the iPhone is just about perfect. I couldn't use a larger phone with one hand. TouchID is it or miss for me, though, which is disappointing.