I read Appointment With Death in play form, and while it was perfectly enjoyable, I didn't love it. I thought it was a reasonably interesting psychological study, but that's about it. Hercule Poirot does not make an appearance in the play, so I'm thinking that the play may be significantly different than the novel.
I like Agatha Christie's novels, but I'm just not sure that her style lends itself terribly well to plays. Of course, I've only read two of them thus far, but I also have not been horribly impressed.