Maybe that's part of it, yes. I mean if I press Cmd+P to look up a source file and Firefox doesn't suggest the source mapped one before the ES5 compiled one, i

Maybe that's part of it, yes. I mean if I press Cmd+P to look up a source file and Firefox doesn't suggest the source mapped one before the ES5 compiled one, it's already beyond me how I should ever seriously work with that tooling. It's just a matter of speed and convenience. But my workflows of course might differ from what others do. With quality I was referring to the actual code quality of Firefox, not so much the interface. See my post below about DOM events changing order when debugging. My instinct just tells me that something is deeply wrong under the hood if something like this can even happen.