Really? IE6 isn't even a tabbed browser. That, alone, would be enough reason for me to send IE6 to it's grave.
Actually, I don't like tabbed browsers. Everyone seems to think it's the greatest thing since sliced bread, but I've never been fond of it. I tend to have quite a few windows open at once, so that means I have to look for the right program in the task bar and then I have to look for the right tab. By having separate windows, I narrow it down to just one step. Also, if I happen to go to a web site that causes an error/issue of some sort and I have to close the browser, it's nice having to close only one window. I've had plenty of instances of losing my place on several sites because of a mishap on Firefox. So, even if I use a tabbed browser, I tend to still open multiple windows (and doing so with Firefox can cause issues...at least for me).
The only problem I have with IE6 is that it isn't up-to-date when it comes to displaying sites. If that could be corrected without having to "upgrade", I would be in browser heaven.