The best forum because of its intimate community. Obviously awful for this reason as well.
This, essentially.
The Atlas is crazy insular. We're kind of hard to find for whatever reason and we don't get sudden streams of new posters like other forums- It's telling that you'll often see "Opinion of x" threads about new members before they've even made 20 posts. This, in turn, has fostered a very intimate atmosphere, including all that is celebrated about this place. But the insularity has led to kind of an abrasive culture (I think partially fostered by the various mines) which can sometimes (though not always) be problematic.
I think a bigger problem is this though- The Atlas attracts a very homogenous group of posters- young, white, middle class-upper class men. Thus, it often suffers from a lack of diversity of viewpoints (underrepresented ones include female/feminist views, and to a much lesser extent, social conservatism), which means that someone with views which challenge their worldview tend to cause an explosion (some major explosion causes in the past include Sandra Fluke and trans* rights).
Still, overall FF. I wouldn't be here if I didn't think so.