Apparently, when this boipic was being made, Glenn Miller's fans were incensed as they felt Mr Jimmy wasn't good looking enough to play the role. However, once it came out, for the most part they did an about face, as the resemblence was uncanny. That is due, primarily, to Stewarts ability to *become* his character. In It's a Wonderful Life, he really is George Bailey - a man who feels he has nothing to live for; in Harvey, he really is talking to a 7ft white rabbit - to the point where you can almost see him, too. This film is no different. He *is* Glenn Miller, with all his lovely Jimmy charm.
There are a few scenes in here where you can tell Jimmy Stewart's laughter is spontaneous and genuine, and for those parts alone it's worth getting the film. The script *is* funny, and both Jimmy and June Allyson (who died only a few months ago) had genuine comedic talent. Once you hear Allyson's exasperated "Well, honestly" you'll positively *look* for reasons to say it, too.
It's a delightful film, from start to finish, notwithstanding the sad ending. In terms of the Stewart compendium, it's a hidden gem. In fact, apart from Anatomy of a Murder, it may be the gemmiest.