This is a fantastic addon, and I'm really enjoying using it. I have a suggestion that could make it even more user-friendly: adding keyboard shortcut for marking the "Start Time" and another shortcut for playing the video from that point. This would make the looping process very easy.

There is no repeat slider in versions 1.0.0, it worked, please fix it, here is a screenshot ! check gmail!

It didn't work until opening a new youtube tab. It usually does what it says it does, but occasionally youtube manages to sneak past it and starting autoplaying a different song. Setting the end time to a second before the end of the video usually prevents that from happening.

Great addon. One thing that could make it even better: keyboard or mouse shortcuts to set the start and end of a loop. Thanks a lot !