It’s really simple: design for modern browsers and make sure IE8 and 9 get appropriate fallbacks. It really isn’t that hard. IE8 won’t get rounded corners, shadows, etc – that should be fine.
IE support has actually significantly dropped for me as I’ve gotten older. My code is cleaner and I have the experience to know right off the bat if something is or isn’t going to work in < IE10 and plan accordingly (like putting in fallbacks right away).