I actually have some information on testing Netflix under Yosemite. This doesn't violate the NDA because it has nothing to do with Yosemite but with Netflix.
I installed Yosemite this morning and accessed Netflix. It still asked for the Silverlight installation. I used their live chat and after the person checked with tech support I found out they are only allowing Macs with a Sandy Bridge or later CPU to run HTML5. I am hoping this is only for initial testing but we'll see.
The following Netflix announcement describes the new features but doesn't include system requirements: http://techblog.netflix.com/2014/06/html5-video-in-safari-on-os-x-yosemite.html (hopefully this won't get stripped)
For those of us who don't know what CPU model they are running, here's a wikipedia site listing them:
http://en.wikipedia.org/wiki/List_of_Macintosh_models_grouped_by_CPU_type#Sandy_Bridge (Core i5 and i7 later than March 2011)