I remember when this first aired it was a big deal, since it actually showed different Klingons, and even a Klingon ship. Also, at the time they apparently thought the Klingons had joined the Federation, since the Klingon bridge shows the Federation seal, but written in Klingon.
This could have been an even better episode, but it suffered from many of the same issues lots of other first season episodes did. They had trouble actually just telling the story, and not stopping to talk too much along the way.
I did really like how they adressed that the alliance with the Federation was painful for the Klingons who were therefore restricted from fighting their greatest foe. It showed how it was basically killing their very soul, being forced to be all nicey-nicey.
It was kind of a nice follow up in the Klingon Civil War when they showed how happy many of the Klingons were to be fighting in battle. Even if it was against each other.