Nigel, The D-Word is planning to become exactly that location "where people go to browse documentary films and watch them in one place." We've got the user base to build this on.
The whole point of Distrify is that the filmmaker (or whoever represents him or her) will be in control of the "marketing and sales drive" you're asking for. And yes, it'll be hard work to connect to your audience. If you don't like to do that yourself, you should consider hiring a producer of marketing and distribution (see our Jon Reiss conference, Think Outside the Box Office ).
I don't know about Journeyman's business model, but they certainly didn't develop their own player that allows for sales happening ANYWHERE on the web, wherever the trailer occurs, and they don't allow for any affiliate system. Distrify developed all that, and that didn't come cheap. Prior to our partnership, we examined their business case and learned that their profit margins are perfectly reasonable.