Jeremy Richey at Moon in the Gutter has a nice tribute to Viva Las Vegas, which just came out in a new DVD (the special features aren't much, but at least the picture is remastered in 16:9 widescreen this time). I've always thought that VLV, and not Elvis Presley's more serious pictures, is the model for what his movies should have been like. The problem with the typical Elvis film isn't that it's too light and fluffy; movie musicals are supposed to be light and fluffy. The problem is that they're cheap, slapdash and nobody involved with the film is doing his or her best work.
That's why Viva Las Vegas is sort of the last of the great M-G-M musicals, because it's the last gasp of a particular type of musical: the short, unpretentious musical that succeeds because of high technical standards and an ability to take advantage of the stars' talents. The producer of Viva Las Vegas, Jack Cummings, was Louis B. Mayer's nephew and he had made a ton of musicals exactly like that: not prestige projects like Arthur Freed's, but films where he was given a star or two and did the best job he could of building an entertaining movie around them. He handled most of Red Skelton's movies at MGM, and then he was given Esther Williams (who was introduced in a movie with Skelton, Bathing Beauty), and had to figure out how to make a successful musical with a star whose main talent was swimming. He did it; he also figured out how to make a 3-D musical (Kiss Me Kate) and M-G-M's first good CinemaScope musical (Seven Brides For Seven Brothers).
The director, George Sidney, had worked with Cummings on Bathing Beauty, so it all came full circle: 20 years had passed, but these old M-G-M pros (and the writer, Sally Benson, who wrote the Meet Me in St. Louis stories) were still filming the same featherweight plots and succeeding because they know how to bring out the best in their stars. Unfortunately, by 1964 almost nobody was making this kind of mid-level musical. After VLV, almost every musical would be either a huge three-hour "A" production, or a cheaply-made quickie for drive-ins. The problem is that the musical, as a genre, couldn't be sustained that way. It needed the people who brought "A" production values to what could never be "A" projects.
Like many people, my favorite number in Viva Las Vegas is "My Rival" -- the song is a big nothing, but Sidney and Ann-Margret do the whole thing in one interrupted two-minute take, with all kinds of effects and stage business to make the number more complicated. It's in the great M-G-M musical tradition of doing numbers in as few takes as possible, with fluid camerawork and precise timing instead of cutting.