I don't have any problems with my DirecTV at all....
DIrecTV, like Dish Network, will shift bandwidth from one channel to another, depending on a formula known only to them. Some channels will look pretty good, while others are almost unviewable.
MPEG2 is the video compression scheme they all use, and it is lossy, meaning the image degradation can be noticable. Most viewers don't notice the degradation, partly because their eye has never been trained to see it.
Then there's the audio. I'm pretty sure this applies to DirecTV also, but with Dish, the audio compression is combined with a peak limiting scheme that causes voice levels to rise and fall depending on the peaks of the music and sound effects.
Network sports and action shows suffer ther most, IMO. 24 is really impacted by that when they play the theme and bumper music while characters are speaking.
There's more, but I'll start sounding like a whiner (might be too late.)