My gut feeling is that the sift would be a bit more stickier if there was a conventional threaded discussion board. Channel Talks have posts that tend to, more often than not, die a death and get few responses.
With a proper hub for intelligent discussion, Channel Talks can still be used to bring up Channel problems/administration issues. Or perhaps dispensed with altogether.
I know some great conversations actually happen in video comments but they are dependent on the submittal of that video. A forum would be a great place to thrash out hot topics or talk about lighter subjects.