It seems to work as advertised, but it'll also steal your focus with one of those "Hey! I updated and I'm so pleased with myself that I want to open a whole new tab to show you!" tabs.

(Really frustrating if you happen to be WATCHING YouTube at the time... which is likely, given that it's an extension for people who care about YouTube enough to install it.)

...as well as requiring you to keep its (otherwise irrelevant) button in your toolbar overflow menu to access the preferences for want of a "Preferences" link from the addons manager.

I'll revise my rating and review if they resolve these issues.