This is an excellent adblocker, probably the best you can find for Firefox and other browsers; it does a great job blocking all ads, and it is also open source, a near guarantee of security and privacy.

The interface is very outdated, though--the buttons and layout are not at all intuitive to less robust computer users (thankfully I'm not one of them) and the settings menu can be confusing to the extreme. Though these problems don't apply to me, they do to many, and I think they should be fixed.

Aside from the UI, uBlock Origin is the best adblocker available for Firefox.