Works as described.
Utilizing it per channel or for specific keywords is a great feature.
Other extensions I've tried have shown the progress bar for a split second when loading, but I have not experienced that with this one yet.

Easily the best addon of its kind. Being able to specify the channels means I don't have to hide the video lengths of videos where the length isn't a spoiler. The addon works instantly and perfectly.

does not work =\

I've tried all other add-ons here and this is the best one out there to not get spoiled.
Big Plus also on the superfast reaction on GitHub.