The picture quality of progressive DVD players is definitely better than that of non-progressive players. The main improvements you'll notice are a tremendous reduction in shimmering and "jaggies" in the picture quality, especially when there is a lot of motion or vertical lines (like a cityscape) in the picture. There isn't any reason, however, to purchase a progressive player unless your TV is capable of accepting the input from one. If it isn't, the picture quality won't be any different.
Progressive DVD players?
I am going to purchase a new DVD player and am considering the Sony S7700 (being discontinued). I don't own an HDTV, or HDTV ready, TV that can take advantage of progressive scan, but I will probably purchase one in the near future. Is the quality of progressive scan pictures that much better? I will use the unit 70% for music, 30% for DVD. I am interest in your thoughts on the different players out there.