In a further version of Kdenlive, is it possible to include a Reverse Video Button ? With this we can do funny movies !

Sxmon

I feel badly the lack of this feature either, not just for fun but cos happens many times I need to reverse a camera panning from a take. In Sony Vegas was as easy as to specify the clip speed < 0 as is -100% for a full reverse

Yea, this is my top missing feature.

http://www.kdenlive.org/mantis/view.php?id=1026
That is what I would wish to do eventually in future.

Of course it'd be very useful, depending on the quality of the frame blending.

That solution is very similar to After Effects' Time Remap function.
In my opinion although there's no doubt it's a very powerful method to set variable speed for a video, it's not the most user friendly way of doing it.

I find the Premiere Pro implementation to be more easy to understand for users. There, the user just sets "velocity" keyframes at each frame, opposed to having to set the clip frame visible at a certain timeline frame.

Besides being more easy to use, another clear advantage of this 'velocity' method versus the 'time remap' one is that with the latter it is almost impossible to return a segment of video to its normal speed, after you have changed it. (i.e. you have to make that part of the graphic to have the 'exact slope' it originally had, and the only way to do this seems to be ...by eyeballing it? With 'velocity' you set back keyframes at 100% value and you are ready to go).

would love to be able to say, "lets rewind that and take another look in slow motion" but obviously there is no reverse video function