It works great and is in my list of must-have extensions every time I have to reinstall firefox. My only gripe with it is that it imposes a fairly big performance hit on websites with a lot of text content, especially social media sites. Facebook becomes nearly unusable if you scroll for a few minutes straight. If only there's a way to disable extensions on a site-to-site basis, but AFAIK it's a limitation with Firefox not the extension dev.