On the plus side - it was great seeing Ben Browder (from Stargate / Farscape) doing a guest spot and the actor playing the Doctor Alien was very good too.
But as others have pointed out, this whole episode has been done before countless times by other superior sci-fi shows. I was pretty much predicting everything that was going to happen, including that the Doctor Alien was a war criminal, because it was so by the numbers and unimaginative.
Now, here's the bit that really confused me, when The Doctor, Amy and Rory first walk into the saloon, the townsfolk ask him if he's the Doctor from outer space and he says yes and then they grab him and throw him over the line.
But later on in the show, Ben Browder says that the Doctor Alien had been in town for years, had treated the townsfolk for disease and even built their electric lights and heaters. So unless all the townsfolk were blind, how did they mix up Matt Smith for an old bloke with green facial scars?
Explanations please.