The first thing Apple has done is to make it compatible with you car, more specifically you can now view you iPhone apps on the built in car display. That is pretty cool.
The next two things, are the automatic things. Siri now automatically knows when she is supposed to stop listening, and you camera automatically chooses when the picture shall be taken i HDR, and all that completely automatic.
Then there is the design that has been changed, changed slightly i may add. As you can see on the pictures below, that are the changes that have been made to the calendar and the call screen. Another design change that I have noticed myself is the caps lock button.
Apple decided to make everything a bit more difficult with the caps lock button, so now you don't have much of a clue when it is in caps lock and when it is not. You are going to get used to it, but in my opinion there was no point in changing that. Try it out for yourself, by downloading iOS 7.1.
Just go to Settings, general, updates and then update.
Baam