"The Empath" was well-done, but the modest "blackout" stage could have been better. When Lost in Space succeeded with this type of set ("The Derelict", "The Magic Mirror"), they created a sense of depth and detail with the clever use of set dressing. And for some reason, the blacked out sets seem more convincing on black and white film, especially as shot by Gene Polito. Color attempts like "Kidnapped in Space" were far less impressive-looking.
On a contrarian note, I think "All Our Yesterdays" was wonderfully realized, and actually benefited from the intimacy of focusing so much on the big three and Zarabeth. A bigger production just wasn't necessary.