I think Heino makes excellent points.
My opinion differs from some of the others, in that I believe we make far too much reliance on digital artifact observations on SD 4x3 DirecTV programming. Way too much. It's not that the artifacts don't exist, or that we shouldn't be concerned with them. No, the problem is that we don't distinguish from where they originate. So the tv set ends up getting blamed for artifacts that are actually within the lower resolution broadcast signal, compression artifacts, and scaling artifacts from the set top box.
So the tv set that makes the less faithful reproduction, hides them behind poor resolution, poor focus, or dithering them comes out on top in a comparison.
I believe if you want to compare digital artifacts imparted on the picture by the *tv set*, you should be observing them where you can eliminate them from the source as much as possible. That means, an HDTV source, HDNet, 1080i, 720p.
Because when you view a DirecTV 4x3 SD channel upconverted to 720p/1080i, you are viewing not just the digital artifacts imparted on the picture by the tv set, but also the artifacts imparted on the picture by the set top box/tuner, scaler, and compression artifacts.
A set top box discriminates between native 720p/1080i and 480p/i broadcasts, letting you scale the 4x3 but not the 16x9. BUT...the tv set makes NO distinction between native 720p and 480i that's been upconverted to 720p by a set top box. From the perspective of the TV set, the 480>720p upconverted signal is just as *native* as the native 720p.
Summary:
When viewing SD DirecTV programming, you're seeing lots of digital artifacts, but how can you tell which ones are in the signal, and which ones are in the tv set?
When viewing HDTV programming, you're seeing many fewer digital artifacts, but the likelihood that the artifacts that you DO see are coming from the tv set is greater.
If we really want the best SD DirecTV picture, view them on an analog set not capable of faithfully resolving all of the offensive details.
Tom