And is 10%+ of the Windows install base really XP???
And is 10%+ of the Windows install base really XP???
I'm not sure about XP specifically, but I get way more than 10% of my traffic from IE6-8. IE8 alone is over 10% on some of my business news sites. Don't forget IE8 shipped with Windows 7.
There's a difference between having certain simpler layouts (although that probably affects conversion too), and IE6 actually messing up a purchase flow on an e-commerce site.
But if it's breaking the flow of your site, it might well be more trouble than it's worth.
I work with some enterprise customers and they seem to be mostly IE8 or IE9. We have one dreadful customer who still wants IE6 support but we've officially dropped IE6 & IE7 support. We still do direct hacks as part of consulting for that customer.
A disproportionate number of our most important users are running IE8. I don't know if it's because they're still on XP (and thus can't upgrade past 8) or some other reason.
I'm not an expert, but I think it's so much that IE9 auto-updates as Win7+ does a much better job of pushing updates that include new browsers.