So I just upgraded from a 46es7100 to a 55f8000 and it would appear that I, too, am having issues with the Smart hub receiving Dolby Digital on the Netflix app and sending it over HDMI ARC. The app itself shows it's only receiving a stereo signal even on 5.1 enabled content when I press the info button or go to the audio settings. Previously, I never had this problem with my es7100 which was set up the same exact way, it was able to send 5.1 from Netflix through ARC to my receiver which was great.
I truly believe this is a Samsung app-related problem on this model of the TV not receiving 5.1 signal. When I watch the same content through my Sony blu Ray player I get 5.1 no problem, and like I said, the TV displays "stereo PCM" when you click the info button so I don't think this is ARC-related (when I watch 5.1 content from my media server through the TV it gets outputted as DD over ARC no problem).
After reading more into the issue, it would seem that this is purely a smart hub issue (hence what thread this is being posted in). The thing that really makes me angry is that my 2011 model es7100 had no problem getting 5.1 from Netflix through the smart hub. When I bought this 2012 f8000, I was under the impression I was upgrading the TV, not downgrading. Now why would I have a silly thought like that?
I'm not sure why Netflix and Samsung would not have addressed this issue by now, this an older TV and has recently been updated to the latest firmware. It would just seem that Netflix is not receiving a 5.1 signal on this specific model through the smart hub. It's a bummer.