How bad is it? It's universally recognized as one of the worst films ever made.
Should you see it? Absolutely - especially in 3-D.
This is a ludicrous allegory of war-torn dissidents in a genocidal endgame - it's also a silly monster movie shot in 3-D. "Ro-Man," a chubby guy in a gorilla suit and space helmet (diving bell with TV antennae, maybe?) gets information from headquarters via a bubble machine in a cave. His death ray will pave the way for the invasion by 268,000 martians, but it doesn't effect the last eight people, who barricade themselves behind barbed wire. The monster than hunts these last survivors down, telling them that theirs will be a painless death from which there is no escape (and then he strangles a little girl). His ineffectiveness is punished by his superiors by the release of a U-ray, which destroys cities and dinosaurs in stock footage (from One Million B.C. and Flight to Mars). Phil Tucker, who also directed the already reviewed Dance Hall Racket, shot this in a reported 4 days in Bronson Canyon with a script reportedly written in 30 minutes and a budget that's been reported in a range from "under $20000" to an unlikely, but possible "$580.25." Much of the film is of a pair of lovers being chased slowly by Ro-Man and is laughable the entire time.