A while back a lot of people where covering how to work around the bug that IE always reloads background images from the server, leading to your UI flickering. Dean wrote one and lots of others wrote the same thing. Today, I saw this simple workaround (from a fellow Googler who worked at Microsoft before):
document.execCommand("BackgroundImageCache", false, true)
Much simpler but makes me wonder why this is not the default setting?