One of the big things to remember is that the software cant create frames magically.
It works sometimes but basically what it does is either duplicates each frame twice to stall it or make a frame inbetween 1 and 2 thats basically both frames blended together mixed with opacity, kinda like in photoshop overlapping one image with another then making if 50% transparent.
Those high speed cameras spit out a shitload of data and you have frames and frames to work with, thats why a lot of the bigger productions like music vvideos/movies etc will use them in lou of the software.
Here is an short, older video tutorial on time remapping:
http://www.videocopilot.net/basic/tutorials/06.Time/