Wow, that's really disappointing, if true. IE9 has been a long time in coming, with plenty of opportunity to test betas, release candidates, and, now, the release version of the browser. Why wouldn't support be available already?
A lack of support for the current release version of Internet Explorer is a serious problem for us, since it's required by many of our large, institutional clients.
I'd love to hear the official word from an ESRI employee. Is IE9 officially not supported? If not, when is a release planned that will support it?