Firefox has improved dramatically since 57 and I'm using it more now, but the one reason why it's still not my main browser is that new windows open too slowly.

Firefox has improved dramatically since 57 and I'm using it more now, but the one reason why it's still not my main browser is that new windows open too slowly. The extra lag can't be much more than 100 ms or so (if that), but opening new windows is the worst possible moment to be a little bit slower than other browsers (on macOS).