Others have commented about Tati's artistry and his sense of humour. I won't add to that.
One thing that many seem to miss is the physical setting for virtually the entire film, which is in and around international-style architecture. Tati continually pokes fun at it, demonstrating how inhumane much of it is in practice. Although idealistic and pure in some sense and appreciated for that (consider Philip Johnson's Glass House in New Canaan), it is often better looked at or visited than lived in.
From one viewpoint, the entire film can be seen as a criticism of that architectural school. It may be the only film that concentrates its energy on architectual criticism.
