Approach separation
The TCAS thread on the technical forum has reminded me of another practical use of the display, assessing the distance you are behind the traffic in front on final. Once established I tend to set the range to five miles and if the guy in front appears on the display it is a reminder to think about how far he is ahead. Obviously depends on the airfield and the expected separation.
If we are asked to slow down, for example to allow a quick departure in front, it bugs me when the guy behind does not react until asked by ATC and then I am put under pressure to expedite clearing the runway. This happens so often I am beginning to wonder if I am doing something wrong. Do you want us all to keep up maximum speed until told to slow down, or is it better to use common sense and not get to within three miles and then ask sarcastic questions about what kind of aircraft is ahead.