The first thing I've noticed when I started the new Firefox was that my start page, which was a quick dial bookmark page, was gone, so I was already ticked off. I've never liked IE. When Netscape came around, I immediately found it to be superior. After Netscape started losing support, I switched to Opera. It was a time of low bandwidths, and Opera was fast.
Firefox came after that as the next big thing. I switched again, and all was good for years. Chrome was a phenomenon. It was gaining popularity so damn fast. Plus, browser updates were now constant. I didn't switch until Firefox started acting up in a major way. Which was four years back or so. Mozilla screwed up. IE comes with every Windows, Chrome is its own OS and is a part of every Android phone. Firefox is almost like Opera now.
