I think, next to being a plain help-forum, PM is a great way to exchange ideas and feedback on existing modules and module-ideas

Perlmonks is a strange beast.
It's largely a newbie-help site,
but also contains a handful of
Things of Terrifying Beauty

-- Erudil quoting robin cited at Terrifying Beauty

This is in stark contrast to SO -- though I've posted a question or two there, I never felt the urge to hang out once it was answered. To me, the SO culture felt cold and disconnected: stay on topic, don't waste time socializing, just deliver the facts.