I use Opera and love it.
I've been using it for years especially to browse Free Republic. The tab capability is especially useful, because its much easier to get control of the desktop when all the web pages are just tabs in one opera session. Sure IE 7 finally has tabs years after Opera and Firefox, but you have to use Windows XP or above. Opera works well on older computers running Windows 2000. Why should I upgrade to a computer running XP of Vista just to browse the web? The only things for which I use IE are Windows Update and E Commerce.