It seems like as the seasons go on, the visual effect angle tends to diminish somewhat. I'm noticing in Season 5, we still have the somewhat blurry shots as the Enterprise passes through, but we really don't have the special effects I can look out for and say, good job CBS Digital. Well, I was watching Hero Worship tonight (I haven't seen this episode in a while, and still think it's a little boring) and the shots of the Nebula are stunning. It's dark, but I think it's a little more creepy than the original SD film.
I'm trying to think of episodes where visual effects will be noticeable for the rest of the season and the only ones I can think of are Cause and Effect, Power Play, and maybe Next Phase (Even though we saw something like that in In Theory). I am enjoying revisiting these episodes though, and actually found an episode that might be really underrated, Violations. Man that episode was creepy, even though I wonder if they could have gone further. Given an HBO format and budget, it might have been a true horror episode.