If you own the original "fat" DVD sets and are trying to decide if you should purchase this, the answer is: Maybe.
The original box sets have more detail, but also have more grain, especially the early seasons. This new set has used a filter to reduce the grain which makes the overall picture look clearer, but also loses some details.I have attached some screenshots for comparison. The first two pictures (from the pilot) show the difference between the old set (left) and this new set (right). You can clearly see the loss of detail on Jack's face in the first, and in the trees in the second, but also the reduction of grain.
However, this isn't the only consideration! The older DVD set is encoded at 30fps interlaced, while this newer set is encoded at 24fps progressive. My third picture of the opening credits shows the difference here. In the original DVD set (left) you can clearly see the banding caused by the interlacing, which is absent from the new set (right). Again, the new set shows less fine detail and looks a little blurred, but also cleaner and with no banding.
So which one is better? There is no simple answer. I dislike the loss of fine detail, but appreciate the 24fps and progressive scan of the new set. I will also add that is hard to notice the loss of detail while actually watching the video at a normal viewing distance vs a still image 2 feet away on a computer screen.
Early seasons of the old DVDs contained only 2 channel audio, while the new set contains both the 2 channel and a 5.1 audio mix for all seasons. The older set contained audio languages other than English, while the new set contains only English audio.
The old DVDs contained only Non-English subtitles, with only Closed Captions in English. The new set contains only English subtitles.
The new DVDs appear to contain the same special features as the old sets, along with an extra disc with additional featurettes.
Other reviewers have reported issues such as incorrect episode order, duplicate discs, and discs "freezing" during playback.
The episode order on the new DVDs is the same as the older DVD sets. This is the "correct" episode order. Several episodes originally aired out of order and thus you find the discrepancy between "aired order" and "DVD order."
My set did not contain duplicate discs, all discs were accounted for.
As for the reports of discs freezing, I did not encounter this. HOWEVER, I believe the reason others have had this issue is because some (not all) of the discs in this new set contain both "Structural Protection" and "Bad Sector Protection," which are additional security features added to the standard DVD encryption. Both of these protections are rare for exactly this reason: They are known to cause playback issues in some DVD players. They are basically intentional defects in the disc intended to fool copy software to prevent copying the discs but they can also fool legitimate DVD players and cause playback problems.
I really wish the powers that be would pay to rescan this show in HD and release a Blu-ray set. Until then, this is likely to be the best set available, and I will most likely be using it over my old set. However, with the loss of some detail along with the (potential playback issues) I I rate it 4 stars instead of 5.