This has been broken for quite some time now, BUT Netflix now has a sweet new HTML5 video player (in Chrome at least) and it was super easy to get working!

I have created a new repo for it:
https://github.com/rtpmatt/Netflix-HTML5-Autoplay-Bookmarklet

And more details can be found here:
http://www.mattevanoff.com/2015/03/new-netflix-autoplay-bookmarklet/