I personally think that Internet Explorer 6 should be outlawed. Web development can be difficult enough to make things look good and work right, that throwing Internet Explorer 6.0 into the mix just makes things that much harder. Even when I'm doing ASP .NET development, you would think that everything would work well with IE 6, but that is not the case.
I spend most of my time using Firefox to test my sites, then do some quick checks in either IE 7 or IE 8, depending on what is installed on the computer, and in most cases things look and work pretty well. Sometimes there may be a few tweaks necessary to get things just right. After that I have to spin up a virtual machine, or find an old computer with IE 6 on it. And that is where the fun begins.
Maybe I'm being a little hard on the browser, but it really is a web developers worst nightmare. If there were only a few computers out there that still had IE 6, that would be one thing. But there is still a large portion of computers that run IE 6 as their primary browser. I defintely favor Firefox, but I don't mind if people want to use IE 7 or IE 8, just not IE 6. We should all wish it a fond farewell, and retire the old chap already.