We share folders with the other writers and producers. I've used for TV Series and a couple feature film projects. The only downside is that you won't know if someone is working on the Final Draft version since it won't open in Dropbox.
My question was more in the line of: How do you administer the sharing - who does what? You as a scriptwriter - do you agree to do scenes, and then share them afterwards, or can you do any writing on documents residing in DB?
My GF and I work on a big project, which uses video, audio, text (also versions... for various reasons) in PDF, .txt, .RTF, Word and Scrivener. In Word, .txt and .RTF DB announces that the document is open, and scrivener has its own announcement regarding "open files". PDF an be annotated freely (in Mac Preview), and sometimes create conflicting copies. Sometimes it also annoying that my GF, who was once lucky to get 50 free GB space drops a 4GB video file on my measly, to the brim ful 9,5 free GB - DB doesn't announce it (it just shows up in the top menu icon, when you click it), and sometimes my beard turns even greyer before remembering the probable reason why DB wont sync.
What has been working great for us lately is breaking the work up and putting in a comment when someone has started working on it and then comment again when their done with there part and upload the latest. With TV it's a bit easier because we usually break up into writing 2 Acts each.
I'd be willing to pay $ 10 a year for 100GB of storage, or $ 19 a year for 200GB. But look, I pay 9.99 for 100GB with all the benefits of Google Drive. I think Dropbox lacks good plans and prices for the general public. Your 1TB plan is good, but who in particular needs all that space? It ends up being very expensive! Let's go! make a good popular access plan! Otherwise they will continue not to be competitive.