I don't have a 5s to give you any firsthand experience. But I know that with some major OS updates, with any system (iPhone, Mac, Windows, Android, etc.) you can always find people complaining about problems. First, no software is perfect, including the operating system you have installed right now. Secondly, people complain online when something is wrong or something changes, but no one takes the time to write comments or post questions when everything works fine or stays the same.
I always try to keep my devices up-to-date as they can and use the latest software in every respect – from the OS to the apps. This way I get the latest features, compatibility, and latest security updates.