Curiously enough, the only two plays that I've done very much revision on were the two adaptations - even though the shape of them was pretty much determined by the original work. With my own plays, the only changes, aside from taking a speech out here, putting one in there (if I thought I dwelled on a point a little too long or didn't make it explicit enough), are very minor; but even though they're very minor - having to do with the inability of actors or the unwillingness of the director to go along with me - I've always regretted them.