But Most people still use IE
Graphene works just fine with IE8 and IE7 with a few design differences like the rounded corners
most of the issues have various fixes if you're persistent enough to make it work.
as for IE6, http://www.ie6countdown.com/
As with things in life, we can't have everything we want in a theme, though Graphene comes close.
If graphene doesn't do what you want it to and you don't want to work hard on it either
then you can use other themes like twentyeleven or twentytwelve.
XP default IE6, XP 30% of the market share. XP only support IE7 IE8, but this theme have some bug in IE7 IE8.
The web site is show for our customer, We Can not ask our customers in order to be able to see my website to upgrade browser!
Graphene was better, If support IE6, It's best!