Some features are highlighted more than others when Apple does one of their updates to iOS, I guess it is simply because they cannot go through all of them. There is one that you may not realise is there but when someone calls you it is not always easy to take the call and you want to let the person know you are going to get back to them or set a reminder to call them in say an hour or when you get to work.
Right now when you get a call it is obvious that you can decline to take the call or answer is as there are two buttons to do this. However, there is a little icon to the right and when you slide it up you get a couple of options.
See the video below to see it in action and how you can customise responses.