Well, I received my set today and though I'd chime in with some early thoughs. I watched Stormfront and Home. The picture quality is QUITE an improvement on the first three seasons. Crystal clear and very sharp. At this point in the series the majority of visual effects seemed to be rendered in HD.
I did notice that I have to get used to the digital look of the show in season 4. It was far less noticeable on dvd. The added clarity and sharpness brings out both the good and the bad. The good being the great detail in the sets, garments etc. The bad being that occassionally I became very much aware of watching actors on a set, something the flawed analogue quality of film seemed to hide more for me.
Still, the show looks very vibrant and I can't wait to watch the slave market scenes from the Augments trilogy tomorrow.