I'm curious. Do you get vote on proposals by the devs? Do you get to put forward proposals? Anyone know?
As others have said, at least 99% of the DDF winds up in the archive. After that, there's the "open discussion" thread (mostly chatter, some discussion about the DDF itself), the "fiction questions" thread (like
Mostly Harmless Questions, but for fiction), and the list of upcoming topics (updated once every few months, with no input from us). Frontier put forward a proposal most weeks, revise it (or not) the next week, then put it in the archive.
It's not yet clear what role the DDF will play now the game is reaching the alpha stage. We've been told to expect some kind of significant in-game thing (many expect the collective to sway the progress of in-game history), but Frontier's detailed proposal is still in the backlog. I would expect them to review the process when they start work on the expansions, so we may or may not get to continue commenting on their proposals.
Joining the DDF this year has got you more access to the developers, but people still had to learn how to make a good argument - I often point to
Extra Credits as mandatory reading. If that continues, reading the archive will give you a good idea of whether the DDF is for you.