Dan M. (Firefox)
I've been using Netscape since v1.1, after switching there from NCSA Mosaic. Somewhere around Netscape 3 Gold, I first used Microsoft Internet Explorer (v2? v3?) which had been a pretty good reason for a good laugh, but nothing more. Things changed with the 4 series: Netscape with it's buggy implementation (if to call it that way) of CSS, it's ridiculous performance and it's lack of useful features over IE made me use Microsoft's product.
Things have changed since then. The constant thread of that browser's integration with the operating system, its lack of useful new features since then (except technologies nobody ever feels like using right now), the pathetic reaction on security threads by Microsoft - all of that simply screamed for a solution. So, there was Mozilla. A great thing when developers can do what they feel like, however with it's memory footprint and startup times, one needed to be pretty masochistic to use this peace of software. I don't really remember when I first heard of firefox/firebird. I downloaded it sometimes around 0.7/0.8 (?) release and never switched back since then. Except having to cheat my bank's site telling I'd been using internet explorer (they refused login to online banking some years ago without IE 5.5+), I didn't experience any serious problem. I've never experienced a virus or a piece of malware on my personal system (except my inbox, but without executing stuff) since then as well. Way before it was in anybody's mouth, I made at least ten persons and two companies switch. I didn't get fired on that decision...
I don't feel like starting another browser war. I know there's plenty of technology published by the W3C that is currently implemented in IE, but any decent support in any other browser I know is missing. As long as nobody including corporate intranets are going to make any use of them, I don't even see a trace of a reason to switch back.