I watched this movie only to hear the Zappa score, which was very effective. Even if Zappa (and everyone else involved) were a complete unknown who had done nothing else, I still would have found the score interesting.
Incredibly enough, though, there were moments when I completely forgot that Zappa was the only reason I was watching the movie and became interested for other reasons. The basic concept was fine, and the script seemed serviceable.
What sank the movie was Richards (in his only credited role) and to a somewhat lesser extent Scott. Most of the movie consists of those two with McCambridge. If their roles had only been acted better, the movie as a whole would be a respectable example of what can be done on a low budget. Instead, their cartoonish performances made it impossible to take the movie as seriously as it could have been.