Weak. This story has been done often. (NBC University of the Air, The Weird Circle, GE Theater...) The best version is probably from Escape. Since it's primarily a mood piece, most adaptations feel it necessary to add characters or business.
Having Madeline in fear of burial alive merely makes obvious what is meant to be a nagging uncertainty.
You know, I think I'll nip out and buy the AIP film version. It's on DVD now paired with "The Pit and the Pendulum".
I'm looking forward to what CBSRMT did with other Poe stories... mostly updatings I believe. I seem to recall liking their Masque of the Red Death.