Due to popular request I have knocked out a mini-tutorial, for the use of speed effect strips in Blender’s VSE.
The Speed Effect strip can be used to re-time video or animations to a new length, or you can reverse the direction of play. Also you can make freeze frames. But best of all you can do speed ramps, that is speed up or slow down the playback of a video strip.
In this example I have not touched on audio speed effects, although you can achieve it with the pitch change value (have a go it’s fun).
While it seems that there is a bug in the speed effect, like it forgets to update when you are keyframing the Speed Factor value or the Frame Number value, you must press the “Refresh Sequencer” button. That forces Blender to check all f-curves etc.