I receive FOX HD via D*and OTA. When I compare the two I see no difference in picture or audio quality. I'm not allowed the DNS feeds for ABC, NBC or CBS so I cannot compare them to the OTA broadcasts I receive.
I wish I could see a Voom broadcast but no retailer one has it set up. I enjoy pay per view, NFL Sunday Ticket, and DVR that Voom doesn't offer. If there is a movie I want to see that is not on D* I will just rent the DVD. It's not HD but DVD's look very good on my set-up.