iOS 7 is a bit buggy on the 5s. I've installed iOS 7 on an iPhone 5, an iPad 3, and an iPad Mini. It runs best on the iPhone 5 and iPad Mini. On the iPhone 5s, iOS 7 is prone to app crashes. Third-party app crashes aren't too awful, but when native apps such as the Settings Menu and Safari crash, you know something's not right.
The hardware is fine, if unexciting. The 5s is a solid little device. Apple designed it with care and everything about it exudes quality and class. The display is great, even if it is smaller than I'd like, and the small form factor makes it easy to carry around and use.
[ For more on the iPhone 5s and the colorful, less expensive 5c, see Apple iPhone 5s, 5c: Pros And Cons. ]
It's not the best voice phone. I've been testing an AT&T model of the iPhone 5s and am not impressed with its phone calls. I heard lots of interference and the earpiece speaker doesn't get quite loud enough. The speakerphone produces plenty of volume, but it also amplifies the interference. The iPhone is a better voice phone.
The battery hasn't given me any trouble. The first few days were a bit iffy, but that's true of most smartphones. Once the battery cycled through a few charges, it settled into a good rhythm. I routinely got a full day out of it, despite heavy use. It's worth noting, though, that the battery cannot be removed or replaced, so you're stuck with what's sealed in the iPhone 5s.
The camera is great. The new software, combined with the improved sensor, go a long way toward making the iPhone 5s one of the best camera phones available. The camera app is simpler to use and includes more features, such as burst mode and slow-motion video capture, and the results are on par with today's best devices. The improved gallery app is far more powerful when it comes to organizing photos, and some of the editing tools are a welcome addition.
iOS 7 is still inflexible. Apple's simple smartphone/tablet user interface may win usability awards, but it is nowhere near as flexible or customizable as Android or even Windows Phone. The inability to control exactly where apps are positioned is frustrating, and the lack of resizable home screen widgets and apps leaves the OS looking too homogenous. I'd love to see some truly dynamic content on the home screen.
Control Center is convenient. Apple's new dashboard for controlling some of the iPhone 5s's features is a big help. It makes simple tasks such as turning on and off the Wi-Fi or Bluetooth radios a breeze. I also like the fact that it includes controls for the music player as well as apps like the flashlight, calculator, timer, and camera. This is definitely a time saver, considering that it took several steps to reach many of these controls in previous versions of iOS.
There's plenty to like about the 5s, but at the end of the day it offers only a slightly different experience than last year's iPhone 5. The Touch ID fingerprint sensor is the biggest difference. The camera and processor improvements in the 5s, though very real, aren't all that much better than the iPhone 5. We can only hope that Apple will make significant changes in next year's iPhone 6.