|Star Trek: The Original Series-Season 1||R4|
Star Trek: The Original Series came out on DVD in R1 little by little on two-episode single DVD releases, beginning in August 1999 and ending in December 2001. Each release had the original trailer previews but nothing more. And unlike this R4 version, the episodes were released in production order, not in the order of the original air date as we have them. These R1 releases are missing out on all the special features, such as the text commentary and featurettes.
A R1 boxed set which appears to be identical to the R4 release is scheduled for release in August.
So, unless you are a purist, and want the NTSC image and the original production order preserved, I suggest picking the whole lot up in the one box set in R4 where the resolution of the image is likely to be a little better than that of the R1 boxed set.