I just got the master of a short film back from the colourist and he has given me, as a DVD master, a version at 23.98 FPS. He says this can be played in both NTSC and PAL players. Since the original was shot at 25 FPS, I asked him if there was a quality loss in going to 23.98 (interpolations etc.) but he said that there was no format change, just that the film will play at a slightly different SPEED.
I'm slightly horrified at the idea of the film being exhibited at the wrong speed, even if it is fairly slight. I make that about a 4% increase in duration or more than half a semitone change in pitch in the soundtrack.
But he seems to think this is fairly standard practice.