Same here. I gave Firefox a fresh chance at v57 (Quantam), but I'm back to Chrome. It was fine honestly, no problems with performance or with what I could do. But Right after install, I spent several minutes in just fixing some very basic UI irritations. It had some extra-spacing on sides of the address bar, a 'heavy' looking menu bar, etc. (most users don't want to do that, and rightly so).

I don't mind the different styled settings or menu items at all. The balance (or lack thereof) between font-sizes/font-weights, line weights, the darker gray lines etc. is what perturbs me. Maybe they should look at making the UI look a little 'lighter', like Safari and Chrome.