Yeah I agree with your assessment ancedotally. Firefox a few months ago had horrible performance in google maps and strangely facebook. I checked again today, it's improved a lot, but it is still noticeably slower for those two cornerstone websites. It was enough to make me stop using firefox again

I'm glad that the perf issues have been improved. They just need to get a little bit better and most objections for firefox would go away. Maybe as a workaround someone could make an extension that opens specific urls in chrome/safari when you open them. Only use chrome for maps and facebook for example :p