My wife and I met doing a professional production of "The Merry Widow" in 1982 -- in English, but a straight translation.
Only the very basic skeleton of the original plot is visible in this "adaptation". Most of the characters have been deleted, along with the entire B plot, and all but one of the characters remaining have been renamed. Most of the characters in the movie aren't in the operetta, either. The action has been moved from Paris to, at first, Washington, DC, and then to the fictional country of Pontevedro, which the movie has renamed "Marshovia", and only later to Paris. The net result is that we don't reach the beginning of the original play until about 45 minutes in.
And the main source of tension in the plot is deleted, too. In the original, years before, Count Danilo and the heroine were very much in love, but his family refused to allow them to marry because she was poor; it's his broken heart that has rendered him a careless playboy. Now that, as a widow, she's the richest woman in the world, she still loves him, and he still loves her, but his pride won't let him admit it to anyone, even himself, and she must spend three acts playing mind games to break him down. The trope of the aristocrat with money problems who won't admit that he's in love with a rich woman for fear of what people will think supplied the main plots of a substantial fraction of Viennese operettas for decades after the 1906 "Widow". In this movie, they've never met before, which rips out not only the heart of the whole thing, but nearly all the comedy.
Lamas does a pretty decent job, though.
An interesting musical point is that several times we hear a snippet or so of "Trés Parisien", an extra song written (in English, despite the title) for the London première, which was not, as far as I know, usually found in American productions until the 1980s or so.
