I am working on a short screenplay and did this before in other programs, but now decided to continuing in Scrivener. I found the best setting for me, using the Compose Mode, Typewriter Mode and a great old fashion typewriter sound in the background while typing. It’s all about being in the right mood and this really does it for me.
André
I haven’t used Scrivener for screenwriting, but I can point you to a terrific Courier font (the standard in the screen and television script writing industry): CourierPrime. I know nothing about Scrivener’s screenwriting capabilities, but the industry standard software tends to be either Movie Magic Screenwriter 2000 or Final Draft. I own both, have used both, and like both. That said, I’m always looking for new ways to avoid work so I may have to try out Scrivener! 
Hope you enjoy.
Adam Rodman