This plugin crippled my browsing experience. Some sites pegged my CPU at 100% with this extension enabled. A great shame because I'm a fan of their search engine, but it had to go. Browsing is now very fast again.

The only other add-on I use is uBlock Origin. If this occurred because they're incompatible, it's uBlock that wins.
Using Firefox Developer Edition 58.0b7 (64-bit) on macOS High Sierra 10.13.1.