Squeenski
Though I don't do much streaming, aside of Youtube, I did stream a couple of things through DirecTV's On Demand service when I first upgraded to Gen5. The things I streamed through On Demand were flawless, and the Youtube videos through current have rarely buffered, only doing so two or three times since I upgraded at the end of March.
One other thing of note is that, with Gen5's increased FAP speed, people have still been able to stream when they run out of their monthly data alotment, though only in the lower definitions. There's no guarantee of this, of course, but it has worked for those who have deliberately run out of data to test such and have written about it.
Just for reference, I disconnected the DirecTV receiver from Hughesnet after my On Demand test as their receivers can use data for things other than On Demand, and due to it being uncontrollable it's recommended that people don't connect a DirecTV receiver to the service.