Large percentage of people still use IE6, I never got why. That thing is full of security flaws, doesn't follow W3C rules, and is long past its due-date. If you ever designed a website from scratch, you know how annoying M$ Internet Explorer 6 is (7 can be pain sometimes too).

Web developers/designers have to spend hours writing hacks so that piece of crap browser rendered their CSS properly. And let's not forget PNGs, that thing will butcher them like there's no tomorrow.

No alpha transparency was really what pushed my buttons. I love shadows, but without alpha transparency you can't get them to look realistic on a background with multiple colors/shades. IE6 will replace alpha transparency with flat white.
Like so:

Of course, like for everything else, there's a fix for this. It involves using DirectX to render PNGs. But this will make your site 2x slower, use-up more bandwidth and it's a real pain to use if you have a lot of PNGs.

If we, web designers/developers stop writing fixes to that beast, people will start switching to real browsers, like Firefox and Opera. We won't have to swear as much and smash our keyboards into pieces.

And if you are IE6 (and below) user, please upgrade to IE8 or even better, switch to Firefox and make your and our lives much easier.