I bought a couple of packs in 1973 and still have the cards (although they are bent up and round cornered to the extreme). I was really into monster films (still am) and thought these were great. I have a complete set of the 1980 series with cards, stickers and 4 different wrappers. One day (it's on my list) I'll get the two 1973 sets and be happy to complete this aspect of card collecting.
Side note: The series is actually titled Creature Feature, but the back of each card has a corny joke or limerick and has the legend "You'll Die Laughing" printed above the joke. Because of this, alot of collectors call or refer to this series as You'll Die Laughing.