I remember when I first saw this in a movie theater. It was a bad print, and the film obviously had broken in a couple of places, as the song "IF" started mid-sentence. The VHS tape, while probably not perfect, has the virtue of being unbroken. I have not yet seen the recent DVD release, but I probably will purchase it.
Diana Rigg and Chloe Franks are the best reasons to see the film, but the others really aren't as awful as some people make them out to be. A good friend of mine was on the set in Vienna, and he told me dozens of horror stories about the filming, one of which was that it was cold and rainy during the scenes in the Vienna Woods, so Elizabeth Taylor caught a bronchial infection which stubbornly hung on during the rest of the filming, as she was not able to get the rest she needed. The company financing the film absolutely insisted that it not run over 120 minutes. Thus, some numbers were cut in the editing process.
It's a shame that we can't have an edition that includes the songs that ended up on the cutting room floor. It's by no means perfect, but it's a lot better than the film musicals of "Mame" and "Man of La Mancha," in my opinion.