This is a hard story to properly judge. Obviously the episodes are missing, and as good a job as has been done trying to restore the story with set pictures and audio, it can't help but take away from the enjoyment. Things like the climactic sword fight between Marco Polo & Tegana can't help but be less effective when you just see som photos of a sword fight and here the sounds of swords clinking together.

The episode still manages to create an intriguing story and has some tense scenes despite this. I enjoy Susan's friendship with Ping-Cho for example. The Cave of 500 Eyes, was an enjoyable set piece. I also like how they build up Kublai Khan for 5+ episodes and when we meet him, he's not this strong, young warrior king. He's a slightly mischievous older man, still powerful just not in the way I was expecting. It's nice the way he bonds with the Doctor as well, bonding with another older man.

Like many of the older serials however, I think this story is too long at 7 episodes. It repeats the same story beats a lot to pad out the run time. Tegans tries to betray Marco Polo at least 4 times, he's thwarted and despite our heroes suspecting he's up to no good, they can never prove it to Marco Polo. Also the Doctor tries to break into the TARDIS to get it up and running multiple times. These aren't bad plot points, but they lose their impact after they've been done a few times.

If this story was a little shorter/less repetitive and could be watched in it's proper format I think this could be a very good, maybe even great story. However as it stands I only really found it decently entertaining.