Just watched 'Lower Decks' and the image on it is, for the most part, excellent - the newer Ent-D is markedly better than the older one used in some shots. The clarity on the PS3 is great.
Then I put in series 2, 'Q Who' and it was still watchable, less detailed and higher contrast. Doesn't put me off. Some of the intermediate seasons have some grain, but otherwise it's OK.
I wonder if the DVDs are 'as good' as the master versions or whether they are poorer copies, or recorded more compressed. Many scenes should be amenable to upscaling with pretty good results.