"Exchange 2010 adds some important changes for non-Internet Explorer browsers by officially and fully supporting both Firefox and Safari with its Premium version of the Outlook Web Access client."
OWA degrades to what I deem a much cleaner client than the version you get if you use IE. The OWA you get in IE7+ uses ActiveX or some sort of Windows-specific JavaScript trickery which is why they restrict it's access to a browser they know will be used on Windows.
I don't really know what WGA is but have seen logos for it in the computer info dialog. I regularly download things from MSDNAA in Chrome, haven't tried the full MSDN portal.