Hmmm. Tough choice. On one hand it's easier to just check one forum. But, at the same time having everything categorized makes things easier to find.
Being a designer, I kinda like the idea of a designer forum, and being a YNOTBob follower, I like the idea of a marketing forum, and I really like the idea of a content forum. I can't even begin to tell you how many times I've looked but not found the content I want.
I would like to be able to help other designes by sharing what techniques I've learned, and I'd like to learn from the pros. After all, the shortcuts, and techniques I've learned are based on tutorials that I've found on the internet anyway. I'd like to be able to show off designs, and get feedback.
I think content, and design are indeed the backbone to the adult industry. We as designers, set the mood, atmosphere, and style to the adult industry.... and of course having kick ass content helps.
However, I'm not sure of the participation level for a design forum would be. Probably not as gooad as, say a content forum, or a marketing forum. But still it would be nice.