Saw the Savage Curtain today and I'd give this about a 8.
Overall fun, a bit outragous. I thought I would dislike Abe Lincoln in space as much as the truck in space on Voyager. But it was just a transmission in the end.
All the characters were interesting that they brought together. I will have to say this though...
Ghengis Khan, Zora, Col Green, Kahless the Unforgettable. Some very evil people, at least from the memories of the crew of the Enterprise. Zora might not have been much of a fighter, or Col. Green (though Colonel would suggest some time in the military.)
And who does the good side get? Abe Lincoln and Surak? Not to mention Kirk and Spock may or may not have been the most shining examples of good. :P
The overall feeling I get after all this was Kahless was a lot of fun to watch. For fans of Vulcans and Klingons we both got a treat. I am a fan of both, so seeing the father of both cultures was fun.
Ghengis Khan is brought in to tell the audience "Ok, now these people are REALLY bad. Now Ghengis Khan we know about you. Don't say anything and let these other three people we don't know get the screen time."
Abraham Lincoln fought off Kahless.

I love it.
Col. Green is fun. Zora basically gave us little to nothing to work with, but then by description she was more of a mad scientist working in her lab than a warrior anyway.
So the fight gets to the point where the pacifist is killed, and the other (Lincoln) is killed off trying to save the pacifist. Leaves a fight for four against two.
Honestly, why did evil loose? One could have kept one of the people busy while the other stabbed them in the back. And what would have happened if they had won? These Excalibans that morphed into these figured would have left home and gone on as these people? Now that would have been a hoot.
Some saw Kirk's reaction to Yarik (Excaliban) a missed opportunity, but honestly, the way the Excalibans treated the Enterprise was extremely unwarranted. Rather than talking to the crew of the Enterprise they conducted a test under their rules and had Kirk and Spock running through a maze to get some cheese or in this case the safety of the Enterprise.
Forget good or evil, how about the Human spirit to overcome? The Excalibans did have good results for "survival" though. Honestly I think the test was flawed. It is like ripping the wings off a fly, telling the fly to fly, and when it doesn't fly conclude the fly is deaf.
Above all, I think that is what this episode illustrates, an poorly executed or conducted lab test. Makes me wonder if the tests we run in our labs ask the right questions or right conditions for the answers we are trying to find.