Rated 2 out of 5 stars
Pros: I still don't know if there's any...
Cons: Doesn't stop or prevent YouTube videos from autoplaying on YouTube site. Useless against YouTube videos embedded on blogs.
It's not meant to stop embedded videos, as those are not supposed to autoplay anyway.
As for not stopping videos on YouTube, make sure you don't have other add-ons that might conflict with it, and try disabling and then enabling the add-on.