Quoted from soren:

Stern has got it right. Why reveal games at a show? Why talk about stuff you are not ready to sell?
No, show up with games you have in plenty and have ready for people to play from when the doors are opened. Let people play and talk about something that is more feature complete. And what those in the know have a bit of an understanding of beforehand. Use your seminar time on a retrospective topic, that people can put into perspective and get more out of.
There seems to be a significant degree of believe within the pinball hobby, that every new game is basically shit. Which waves off when people actually see the game in the flesh. And when code, rules and display are more up to snuff.