I love Firefox and have always preferred it. However, the latest update which causes the back button to disappear (you have to slide up from the bottom) is stupid and not something I can imagine a lot of people have asked for. The silly goal of trying to maximise screen space at any cost results in a very poor user experience. People always want to go back and forth between websites and making it harder isn't the way to do that. This + the change to websites being in groups = bad UI