As you will have guessed from it's title, this is indeed a spaghetti western based on Hamlet. Unless you are illiterate you will know the story, and a lot of the fun stems from seeing how this version differs from the play.
However, most everything else is quite cheap. True, the cinematography is fantastic, but even visually it got clumsy - there is a scene where Johnny is bent over and the camera circles his upper body in a manner that almost makes it seem he has no body at all. And there are plenty of more mistakes like this.
However, the technical aspects is the least of this films problems. Johnny Hamlet's biggest problems are: The Acting - random smirks and incomprehensible behavior. Gertie see's her son, looks at him for a long while and then he disappears. A few seconds later she says "Who's there" and then in the same breath - "Johnny(wait)". Just a few seconds later his uncle comes out, give a few lines, looks at him for a while, for then to shout "Johnny" like an hello. + Lot of moronic smirks like "hey I'm the bad guy, you should know that".
The Plotting - People seem to know everything. For example a person rides out to find someone this person has no way of knowing where is, however the character had apparently read the script. And lets not forget a disappearing circus troupe. And why the hell do they let the bad guys go every time they try to kill them. "Oh that's OK guys, we'll talk to you later". Jesus.
As stated, it's strengths/entertainment value lies primarily in the fantastic cinematography and comparing the film to the play. But this film is, at least to me, too damn dumb.