It's funny as, though it is a really simple complication, it remains a very appealing one. As you say, because of its romantism maybe...
Here is MY moonphase watch today:
I must say this Patek MP disk fits very well the Nautilus but I don't really like it on classic Pateks. I think that a classic watch should be given an engraved or 3D-painted or more decorated moon. Just a thought.
And here is, with De Bethune, one of the MP display I find the most beautiful (VC Patrimony Chrono-QP):
Cheers, Mark