I had long heard about the "Fidel Castro episode" of TWILIGHT ZONE, and finally watched it last night. Yes, it is a bit heavy-handed, but I still enjoyed it. Peter Falk was always a likable actor, and he is very effective as the maniacal dictator. The setting of the Baroque hall in which the entire episode takes place is realistic and effective, resembling the colonial architecture you often find in Latin America. You can practically feel the tropical heat, the sand and the grime. In addition, it was a pleasant surprise to see Will Kuluva (with whom I was previously familiar as "Mr. Ferguson" in the hour-long episode "The New Exhibit") as the outgoing leader of the country. Kuluva had a fine speaking voice and presence. The episode has a notable musical score - surprisingly including a harpsichord, suggestive of a crumbling Baroque façade.
Some other reviewers here feel that the appearance and accents of Clemente's henchmen reflected negative caricatures of Latinos. The actors appear to have been a mix of Italians, Greeks, Jews and one Hispanic. I found their portrayals above all to be a caricature of unkempt militant leftist types. "Latino" did not exist as a racial category in 1961; these were "Latin Americans." Audiences were not ethnically and racially hypersensitive back then, as today.
I do think Serling missed an opportunity with the priest character. Priests, in addition to moral authorities, are also agents of mercy and forgiveness. It would have been not only effective writing but obligatory pastoral practice for the priest to try to lead Clemente to repentance and confession - and explicitly to invoke God! - before he killed himself. The priest seems little more than a "preachy" plot mechanism.
On a final note, I am happy to see that Rod Serling was a liberal in the classic sense and was anti-communist, indeed anti-tyranny of any kind.