I finally got around to making a few tweaks to the videos created on WebPagetest.
The most obvious change is that each page has it’s own timer that stops when that page completes: http://bit.ly/iib7RW
The infrastructure was put into place to also allow stopping each page at a different time than the default fully-loaded time - hope to have that exposed in the UI soon so you can have them stop at onLoad (or even specify the end to be when the above-the-fold finishes rendering).
The videos are generated from templates with a pretty flexible language (AVISynth) so if you have any suggestions for improvements just let me know.
-Pat