I've been happy with everything about Firefox (on Xubuntu) from many years now. But when they released Quantum, the thing that bothered me a bit was not any feature or performance, but them removing curvy tabs for rectangular ones. Rather shallow of me, but we all have our UI quirks :). Luckily, Firefox UI is very customizable and somebody had already put in the effort [1] to provide curvy tabs. Just had to download it, change the RGB() values therein, and got back my preferred green curvy tabs. Just a silly thing, but might give somebody one more reason to switch to Firefox.