To start off, this happens to be my favorite of the ST OS.
In addition to StuOz's critical comments I'll throw in some more: Getting technical, when the Enterprise fires it's photon torps at a blind target, they'd have to be mighty close to direct hits (I believe) in order to cause any disturbance much less damage to the Romulan vessel with the vacuum of space to contend with.
I had somewhat of a problem with the Romulan commander questioning his faith in the Romulan "protocol" or their leadership, unless it has to do with attacking vulnerable targets (outposts in the neutral zone) that are not at war. Also, I don't think commander would fall for the basic, or simple tactics that Kirk played, such as "playing dead," or falling for the ploy that the subordinate puts on him about whether or not to attack the Enterprise when it is playing dead.
On the Enterprise: I'm surprised that after seeing the Romulan vessel's method of attack earlier, that Sulu would say, "Are they surrendering?" when it attacks the Enterprise the first time.
Funny how Spock can only get the repair done on the weapons control right when the emergency is over.
Also in the final attack, I thought the Romulan vessel was uncloaked too long (so long that Spock could run down a couple aisles and back to the weapons room and activate and fire the photon torpedoes. I would have used phasers at this point, but I'm sure it had to do with the technicians and budget).
On the positive side: It's a good drama played on the Romulan vessel, in which to introduce us to the Romulans. Great scenes with Stiles telling a good deal of the human knowledge of the Romulans. Also his conflict with Spock is right up there. I wished Stiles' character would have stayed on the show for a while, if for nothing else than the energy he added.
It's only in fun that I point out the negatives and goofs, (I'm sure there are more). But for me this is as good as it gets!! "Balance of Terror" is always the one I place at the top in my ST rankings.