I'm new in the last 6 months.
My impression of this site is that the members do a fantastic job of finding great articles and posting them. I can stay on top of anything I like on this site.
The discussion is pretty non-substantive, though. I characterize responses as either short quips or rants. Like RedWing9, I pick the article, read it, and then maybe read 4 responses, and then move on. I rarely engage in the discussion.
I was part of another forum that went this way--lots of really great discussion, the site became more and more popular, and then it disintegrated. My opinion is that if the people who engage in really substantive debate leave a forum, there is no one left to show others what the forum is supposed to be.
I agree with you. And the debates were really great on here a few years back (There is nothing more brutal then interideological warfare.) There are still some pretty good ones now and then, but they overwhelmed by poorly articulated posts filled with logical fallacies (ad hominem's and the like).