I use IE6, Opera, and FF. There are sites that do not open properly in Opera or FF but do so in IE (and vice versa). By adding yahoo toolbar you can get tabbed browsing and other features similar to FF and Opera in IE6.
I agree with you on that. When I was designing my site I found it didn't work with FF and had to redo my CSS.
I'm using IE7. I like it just fine. It has the tabs like FF. I don't know what the big deal is with tabs, but they seem to be all the rage! And IE has them now...
I use IE7, it is just fine firefox takes up too much ram, as well as netscape. Any reason why I shouldn't use IE?
I find that Firefox sucks balls. I'm like one of them old fashioned peeps that grew up with IE so still use it to this very day.