Actually greg, the screenplay doesn't need to be formatted at all although that is obviously desirable to make it easier on the eyes of the poor readers who have to wade through hundreds of scripts a week. So we push that, but it's not 100% accurate.
However, it does have to be engaging, have proper arcs, have a one page or less description of who you're targeting and where you see the story heading (after it's polished). Believe me - we've taken junk ass scripts that looked like they were put together by a dyslexic on a Commodore. We've also bought a stapled together compilation of cocktail napkins, complete with olive juice stains.
Get the story right, or at least flesh out the ideas somewhat and be willing to cede total control to someone more professional than you, and you're half way there.