This is definitely one of the best kung fu movies ever, and may be one of the best movies ever... It's got a great plot that functions like a puzzle, with lots of intrigue and suspense. This film is full of cat and mouse games and deceptions, with people hiding their identities and their natures. The characters in this film live and breath much more than your average kung fu movie characters. They are all interesting and compelling and the movie does a good job at giving them scenes to show their personality's and desires.
The fight scenes play out like little stories and many of them are very original and exciting. It has cool training sequences and martial arts skills that are so awesome they enter the realm of fantasy. There are 5 members of the poison clan each one with his own style that mimics the special skill of a venomous animal. The styles of each of these characters are fun to watch and you can see the techniques they use in training applied during the film... When this happens, The director uses quick cutting back to the training scene to draw a parallel. These cuts are accompanied by music changes and sound effects and the whole thing really works nicely.
One thing about this movie that is very original is the way it treats death. The director Chang Cheh was obviously very concerned that the film not trivialize death. This makes some of the scenes in the movie much more effective. We actually care when people are killed in this film. This is because the camera lingers on the horror of death even when the bad guys are killed. Some of the sequences in this movie are truly gut wrenching. When characters go in search of vengeance you really feel their anger and pain.
At the same time, this is also a fun movie. It has all the typical things you expect from a traditional kung fu film. There is bad dubbing, The characters are willing to fight at the drop of a hat. Some of the sound effects are hilarious and at times the behavior of the characters is incredibly unrealistic... all this just adds to the greatness of the film.
And lets not forget that this director was a visual stylist much more gifted than most of his contemporaries. If you watch this movie closely you will notice that the technical prowess on display is virtuostic. Everything goes by so fast (because of the quick cutting style and the rapid camera movements of the genre) that it is easy to overlook how beautiful the movie really is. The lighting and composition are spectacular at times. The camera work and movement is extremely sophisticated along with very interesting fast paced editing... In the scenes that portray suspense and intrigue for example, imagine Hitchcock moving at about twice the speed. Chang Cheh was truly a master craftsman and artist who knew his genre and was able to produce important material while working within it's confines. He doesn't rattle the boat of the kung fu genre film, but in a subtle way his skills permeate every scene and every shot and they add greatly to the quality of the work. He is an important filmmaker who continues to influence many people.
This is the real package A kung fu movie that delivers on every level. It's art, it's trash, it's emotionally moving, and it's fun, it has a true sense of morality, but doesn't allow that morality to get in the way of delivering good action. I recommend it to everybody whether you are a fan of this genre or not.

The only thing I remember about this movie are two things: first, as a twelve year old, even I thought it stunk. Second, it was so bad that when Mad magazine did a parody of it, they quit after the first page, and wrote a disclaimer at the bottom of the page saying that they had completely disavowed it.
If you want to see great sophomoric comedies of this period, try Animal House. It's so stupid and vulgar it lowers itself to high art. Another good selection would be Caddyshack, the classic with the late Rodney Dangerfield and Bill Murray before he became annoyingly charming, with great lines like greens keeper Carl Spackler's "Correct me if I'm wrong Sandy, but if I kill all the golfers they'll lock me up and throw away the key."