nearly awesome Rated 4 out of 5 stars
Works great, I can open multiple tabs / windows / players and they won't start playing until I'm ready for them.
Note: it does interfere with YouTube Video Editor, so simply turn it off when editing videos.
As of October Youtube had changed it's code, but the programmer has provided and upgrade that works (go into comment section to see his response and link - the upgrade works despite not having yet been reviewed by Mozilla)
Thanks Steve. I should turn of the extension on editor pages. Will add that in next version.