I’d listened to Agatha Christie’s Appointment with Death as a radio play and been badly puzzled by the ending, because I thought the ending was different. A commenter going by “creepygirl” pointed out that Christie adapted the novel for stage, removing Poirot and changing the ending to what I remembered (so, err, don’t read the ROT13’ed text in that post if you don’t want to know how the play comes out). I re-read the play today over lunch just to see how it compared.
I agree that the play’s solution is better; I find it more emotionally satisfying and less snobbish about class, or at least less suspectible to a reading that it was snobbish about class. In fact, the play takes a class thing that was annoying me and turns it neatly on its head, which I appreciated. The proof of the mystery is a little lame, but on the whole I do think Christie’s rewrite improved the story (which is not always the case, e.g., And Then There Were None).