My understanding is that as long as the NAS has an iTunes server (and many do these days), it should be able to stream content to Apple TV, etc.
The real point of the video, though, is setting up a system that allows you to use your iTunes in the same way you always have for ripping, downloading and syncing with iPods, as well as centralising your content on a device that will keep it safe (assuming you're sensible with your choice of NAS) and allow it to be accessed at any time from any other player on your network (think Sonos, LaCie, Boxee, or any number of new TVs and Blu-ray players).
Think that answers your question, but shout if not!