When can I install this on my trusty and stable XPsp3 box? Oh...I see...guess it's the Fox (or Chrome or Opera or...) for me.
As for updating the sites...MS can piss right off. They're coded to standards and render perfectly in all browsers bar IE. I have put in a few tweaks to make them acceptable in IE, although some of the rendering still sucks ass. If IE9 can't cope with the same HTML as everyone else, then I will have to charge clients for the extra work (as was done with the initial IE fiddling); not that I expect any of them to upgrade...they're still on IE6 FFS!
(I don't do public facing websites - I get a lot more input on how things will be. Oh, and my client 'get' the whole standards thing, many rue the day they allowed ActiveX plug-ins and other crap as they are now stuck).