Something I just now learned about iOS 7.
I upgraded my iPhone 4S and iPad 2 literally 2 days before 7.1 was released. I never really had any interest in iOS 7 until apps started requiring it. So I didn't learn all the new bells and whistles until after I upgraded.
Anyway I just learned that in iOS 7, when you kill an app (swipe up,) it also kills background Location Services for the app. In previous iOS versions, background Location Services would still run as needed even if you force-closed the app.
So say you tell Siri to remind you about something when you reach a certain location. In iOS 7, you must now keep the Reminders app open for it to work. If you kill the app, it will not track you any longer.
iOS 7.1 restored Location Services back to the old way.
Me personally, I'm not sure which I prefer. I like the idea of "killing" an app means it literally will not run anything now, but I've been in the habit of killing unused apps for a long time now, so I will have to remember to keep apps open that I want to use Location Services with.