And, having said all that, yes, openacs is -big- with lots to learn and such. Overall, it's for big sites like amazon and like that. See:
http://photo.net for a real example of the collaborative features of the original ACS (ArsDigita Community System).
I'd say work with it for awhile... see what you think, and see how easy it is to customize. Keep going thru the tutorial; I have an unobtrusive solution for the content repository thing, I'll look for it
