For more details, please refer the news announced by Apple official:
This update contains improvements, bug fixes and security updates, including:
Further improvements to Touch ID fingerprint recognition
Fixes a bug that could impact keyboard responsiveness
Fixes an issue when using Bluetooth keyboards with VoiceOver enabled
For information on the security content of this update, please visit this website:
Actually, what iOS 7.1.1 brings on iPhone 5S is not all, iOS 7.1.1 also improve:
1. Battery life: it is much more stable than before.
2. Applications: applications like WhatsApp, Twitter, and Instagram are performed admirably.
3. Network: delivers quality LTE and Wi-Fi connectivity.
Be aware before install iOS 7.1.1
Take your time, before update your iPhone 5S to iOS 7.1.1, look back what bad thing happened the last time you update iOS. Yeah, it is easy to lose iPhone data like contacts, bookmarks, photos after iOS upgrade. Moreover, data lost also occurs after jailbreak iOS 7. Therefore, it is very necessary to backup iPhone data before update!
Unfortunately, you forgot to make a backup. That’s ok, you can find out how to get back lost data iOS 7.1.1 in this iPhone 5S data recovery blog.