I have an easy metric for that: when you're navigating, look at the "loading" spinner on the tab bar, and see how it almost always freezes every time a page is

I have an easy metric for that: when you're navigating, look at the "loading" spinner on the tab bar, and see how it almost always freezes every time a page is being drawn. DOM painting/manipulation times in Gecko are a joke, probably the worst pain point of Firefox. And it's not the only one...