Pro The extensions from the chrome store is also available on firefox & waterfox
If using a script manager it is usable across a whole range of browsers. There is a free script available to be used in browser script managers like ''Tampermonkey" which includes all functions of the addon through the script injections.
Con Iridium is currently on hold
The current build includes a bug which seems to break youtube functionality. However after a bit of searching, a solution can be found. Posted here to help others who might be debugging all their extensions for youtube not loading videos.
The solution for many seems to be to keep the autoplay function within Iridium settings ON.
Now your videos will most likely load and play again like they should.