Starting to watch DS9 from the beginning. It's amazing how there is so much depth to all the episodes and stories. Love it!
I think this is true of much of Trek. I definitely liked DS9 and ENT more the second time around, and I had enjoyed them during their original runs as well. I definitely tend to notice more when I am watching the 2nd time.
I recently finished watching DS9 for the second time too and I also thought it got even better. I didn't appreciate the whole Dominion thing the first time but it grew on my the second time.