"Mr. and Mrs. Smith" is one of the not too well known early American Hitchcock's movie. But if "Lifeboat" (wich unfortunately also belongs to this category) is an underrated masterpiece, not all the movies signed by the master of suspense in that time (the early 40's) are really worth seeing. And to tell the truth, not discovering this film isn't really a lost.
"Mr. and Mrs. Smith" is an average and conventional screwball comedy, where it's rather hard to find the Hitchcock's touch. Maybe you can catch a glimpse of his shadow (wich isn't much) in the cruelty that Carole Lombard is sometime capable of (but it's well hidden in an impersonal package), in a vertigo scene where two of the characters are trapped on top of a trade fair attraction, and maybe in the character of the mother. And that's about it ! Even for the Hitchcock fan, there is little to connect with.
And for the screwball comedies amateur, there isn't very much more: none of the situation are exaggerated enough for being really funny, and we're far from the masterpieces of Hawks for instance. And if one or two scene are quite amusing, there're not even the funniest in Hitchcock's filmography, who created comical situations in almost all his movies (even "Psycho" could be considered full of very dark humor). So, there is really little to save in this movie, that can without annoying anyone (or maybe only both hardcore fans of Hitchcock and screwball comedy, who are in love with Carole Lombard), stays one of the not too well known early American Hitchcock's movie.