IMO, the "trails" function, whichever sim game thought of it first, is the best function for tactical analysis of all the film viewer functions.
Our country does not speak English, and we've never been in WW2. So naturally, getting ACM/BFM material from even the internet can be difficult for some people. Under these circumstances, I sometimes use the 'trails' function in the film viewer, and use it to create small AVI video files to help explain various maneuvers and stuff.
For the beginners of the game, they seem to more often than not get confused when multiple plane engagements happen and trails are all over the screen.
So, a very very small, practical wish:
HT, please give us the ability to change the colors of the trails... so player plane can use the red trails, and one can designate the color of the trails of other planes.