I keep encouraging people to use Firefox over the others. My efforts keep failing. Mozilla’s focus on privacy is important and should be to others. People have been burned in the past and are willing to give up privacy for something that just works. The irony.
Font rendering looks non-native on most platforms.
Scrolling behavior seems non-native on most platforms.
The combined location/search bar seems slower, and gives less useful results, than the same feature in other browsers.
Inferior developer tools.
Mozilla's marketing portraying itself as the white knight of the open web is tiresome and contradicted by past behavior. Pocket is still installed by default, and remember the Mr. Robot scandal?
Tracking is easily defeated in other browsers. Besides, if you use Gmail and Google search, and watch videos on Youtube, you've already decided to give your data to Google and you might as well use Chrome too.