Senses of Cinema calls it "deeply felt, and unerringly personal". Salon.com says, "lyricism seems to be Truffaut’s natural language". OpenCulture.com has an article that opens with this:
By the French New Wave’s standards, François Truffaut made films with a startling straightforwardness. Yet something about the man’s entire body of work feeds the sneaking suspicion that, no matter how many times you’ve watched everything in it, you’ve never gazed upon its depths.