I didn't bother to get the vid because my default is winamp and I can never see the videos in winamp just hear the sound. Anyways......for killing goons or tyrants with the saw you would normally be on defense. I.E A tyrant is charging into the base to take out a vital structure like a Defense comp or it is simply killing turrets. If it is killing turrets rev up your painsaw and rush into it cutting its chest up. If it charges into your base to kill the def comp you can simply get behind the tyrant and start sawing so it cant backup and if It turns around it should be dead by then( base defenses,other humans, your saw). If you want to see me doing this you can always go by beeergarden its the main server I play on.
It's a demo, not a video. You put it in your tremulous base/demos folder (make the folder if it doesn't exist), then in-game pull down console (~ button) and type /demo filename, in this case Chainsaw.
Also, you DO know it's "painsaw", right?
Edit: wow, the video is just Belier and Apika teamkilling their entire base with painsaws. They don't even kill a single alien, and the demo lasts about 1 minute. Can a mod delete this, all this thread is is Belier trying to make himself sound skilled at Trem.