btw, regarding UI and extensibility, a suggestion that many advanced users want to give is: look at Vivaldi ;)
But it is no real browser and only an advanced web app bundled with Chromium. Also, smashing a wrapper on top of Chromium with features and call it a day is one of the most stupid things ever which a group of developers can do.
But Vivaldi shows what guys do when they have respect of power users. They add features we want and we prefer and not only features what simple users or Chrome users want and prefer.
Firefox started working on many features for power users (look at testpilot’s vertical tabs), but let’s hope they#ll do more.
Why people value simplicity and minimalism and design more higher today than having customization features and options?