Scaled resolution is default on most/all retina MacBooks which is unfortunate.
For me it is only slow if I go outside the default scaled resolution. On my 2015 13" mbp I use the default scaled resolution to get around the performance issues.
Another work around if you want to use a non-default scaled resolution with firefox is to use firefox in non retina mode. I prefer not to use this as it makes the experience blurry.
I do wish they would fix this issue though.
Oh ok, great. For me the default scaled works best visually and I don’t use an external monitor so glad I won’t have this issue.
With the handoff working too I’m downloading tonight to give FF a fair shake.
That seems to be a known issue, but for some reason it's taking a long time to be solved.