So, Firefox is now on around 100 million computers, worldwide. And it's only been out "formally" for a year.
I've used both Firefox and Internet Explorer, and with the small exception of a few superficialities, I don't see a lot of difference between them. If there is anything about Firefox that is universally agreed upon as being better, it's hidden and subtle to me.
Don't get me wrong, I like it. But I seem to get more pop-ups while using it than when I'm using Explorer, at which time I get no pop-ups. That's a big difference to me.