I'm glad this is moving to Firefox-only for the developer to be able to work on it easily. Firefox is easily the best browser right now, considering Google's obstinacy surrounding public-standards-compliant API implementation in their flagship browser.

This extension has been essential for using YouTube, especially for allowing me to control volume with the mouse wheel, like any normal video player. I hope that feature is next on Particle's list to reimplement in the new refactored version. They are doing a great service to the community by continuing to develop this awesome browser extension.