I remember when these came out in 1999 but I never got them because I didn't have DVD at that time.
I can imagine that these "earliest" DVD releases would be quite collectable today. Say what you will about the convenience (and saved shelf space!) of boxsets, but I've always thought individual releases of TV shows have got a greater collectability factor. They look great all lined up together on shelves too!
The Star Trek DVD Files also released individual discs with the episodes in production order (three episodes to a disc IIRC). I saw the one for 'The Trouble With Tribbles' at a local thrift store no more than a few weeks ago.