I much prefer to have the option exposed in the UI, but you can do this with any...

I much prefer to have the option exposed in the UI, but you can do this with any HTML5 video element by setting the video element's playbackRate. Often, it's as easy as 'document.getElementsByTagName('video')[0].playbackRate = 1.5'. I have a bookmarklet that does exactly this, so I love to see HTML5 video being the default more and more.