I was aware going in that it was, to that point in his career, Corman's biggest box-office hit. It's easy to see why. Viewed today, understanding a little about North American film history, Attack is appreciated for what it is and tries to be -- pure unaffected movie matinee entertainment. While not without flaws, the flick is propelled to its inevitable conclusion (guess who wins), not only by director Corman, but through brisk scripting courtesy of the ever dependable Charles B. Griffith. This may be the film's real flaw although one common for feature films of slight running time; Attack is 62 minutes long. With a single-minded propulsion there is little room for anything else, story-wise. (Young people attending the matinees and drive-ins would not have cared too much. Also, I can think of a few recent films that would benefit immensely from a 62 minute "cut".)
(I popped out of the film just once the other night: Russell Johnson plays a couple of sequences without wearing his shirt. The actor said in an interview years ago that while auditioning for the role of the "Professor" in Gilligan's Island, he was asked by the show's producers if he would mind taking his shirt off... to see what he would look like without his shirt on. He was not too keen on the idea.)
I'm not suggesting that Attack of the Crab Monsters is a great film, but: A friend told me a few years ago that he cares not for intellectual art... he just wants to be entertained when he goes to the movies. I'm tuned a little differently than my fast-food pal, but I could give him an answer in regards to what was in my bowl two nights ago: "Yes, I was!"