At http://people.mozilla.com/~prouget/ie9/ there is a very provocative article entitled "Is IE9 a modern browser?". There is a rebuttal by Tim Sneath at http://blogs.msdn.com/b/tims/archive/2011/02/15/a-modern-browser.aspx that is well worth a look.
Certainly IE9 is already superior to its predecessors.
My comment on the matter is that those that consider IE9 to be non-standards compliant, should submit tests to the W3C to demonstrate the non-compliance. Upon acceptance by the W3C, all the competing browsers can then be re-tested. I prefer objective tests to subjective opinion.
I have used IE9 and on some sites such as Hotmail, it is noticeably faster. I have so far been unable to apply the promised IE9 lockout of spyware cookies. With Firefox, I just instal NoScript and never enable spyware sites.