Sleeper was a very interesting project for Allen. He had spent time doing stand up, and up until this, his movies had been written around the jokes. With the exception of Play it Again, Sam, they were a series of sketches loosely tied into a weak plot. Sleeper was the beginning of the end of this. While the plot is somewhat "sit-com-ish", it was still there, and viewers always kept it in mind. It was also loose enough that Allen could incorporate scenes paying homage to the early silent film stars (the scene with the flying suits is my personal favorite). Miles Monroe was also a rip off from Bob Hope's cowardly hero personalities, but Allen gave it his own twist, and, in my opinion, made it much better. All in all, Allen achieved the perfect blend of slapstick and substance for those in need of a simple comedy. It lacks the depth of some of his better films, but if you want to laugh, this is for you.
Oh, and if you find it somewhat intellectually devoid, try Love and Death. It was his next film, and he added less slapstick and more highbrow comedy, as well as a little more real drama and substance.