This episode was very good throughout the entire episode. It was cleverly plotted, well-acted and had interesting social and moral issues that trickled out through the plot. I am impressed by this episode and it showed some nice growth on the part of the writers. The way they crafted the 'Setal' character, one was never quite sure if he was lying or not or whether he was a spy or truly out to prevent a war. His character was interestingly written.
I rather prefer that the Romulans are back in Star Trek during that era. Its also a pleasure to see Tomalek again even though it was so soon after “The Enemy.” Tomalek makes a good adversary for Picard.
"The Defector" was a step in the right direction for TNG.