Using MySpeed is simplicity itself. Start the program and then visit a video site. When you want to change the speed with which the video plays, just move the slider to the proper speed. That's all it takes.
Keep in mind, though, that the sound gets sped up or slowed down to match the speed of the video. At very high speeds the sound may suffer from the "chipmunk effect," and at very low speeds it may suffers from a monster-voice effect. MySpeed's developer says steps have been taken to minimize those effects, but they're still noticeable. Transcibers should note that slowing down the speed moderately distorts the voice only slightly, so that it's still suitable for transcriptions. Slow it down too much, though, and the voice is hard to understand.
MySpeed works only with sites that use Flash for video play. YouTube and most other video sites use Flash, but there is a chance that it won't work with every site you come across.
The only serious drawback to this program is its price. At $30, it doesn't come cheap. It may not be worthwhile to pay for it if all you want to do is get through ads quickly. But for those who need to transcribe from online video, MySpeed may well be worth a shot.
Note that there are two versions of this program: MySpeed at $30, and MySpeed Premier at $100. The Premier version does everything the standard version does, and also allows you to save videos and view them offline.