Ever wanted to slow video down or even speed it up, say for timelapse? Then check out Blender’s Speed effect in the VSE.
While I made it seem like there is a bug in the speed effect, forgetting 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.
Sorry about that.