the 84 version i downloaded was in chinese.what a hassle.at least the 85 is in english.i couldnt upgrade from the chinese one,had to do a clean install.it was good to get rid of the rest of the chinese that was left though.
i have tested both x64 flavour and i don't see any differences... if exist any diference it is very minimal...
I would go with - updated WDK and maybe some minor bug fixes too. Just my speculations. Oh, and the subversion incremented by one