Tried that some time ago. And somehow I didn’t feel comfortable with it. At that time I continued using Final Draft. Just after reading about it again, I got it again and after toying with it for a couple of minutes I discarded it again. It is an amazing piece of software, no doubt about that. If someone is not satisfied with Scriveners scriptwriting features and would like to have something especially welded to meet the producers demands, go for it. It is, after all, free. And before you buy Montage or Final Draft…
I currently don’t have any unfinished scripts, thankfully. And I do know Final Draft; something about Celtx simply doesn’t feel right; maybe its because you can do too much, from the authors point of view. In my experience while writing I don’t care about props and stuff.
Nevertheless, I would like to see all its production features in action, for real. Maybe later this year I can check that out.