I use IE and Firefox interchangeably. Some things work faster on IE and some things work faster on FF. IE does start up faster than Firefox, though. I hate Opera due to it's ignorance in some of the standards like page margin and transparency. As for the link above the "acid2" test failed worse in IE7 Beta 2(just downloaded it), worked a little bit better in Firefox, and worked a little bit more in Opera. As a web developer, I test all my pages first in Firefox, then in IE, then in Opera.