For me, home is JD. There just isn't a better bunch of customizers and custom junkies out there. I have yet to find any other place that has the kind of thoughtful and constructive feedback people will give you here. I also think JD would be far more willing to cut the head off a snake trying to poison the atmosphere.
Finally, I really love how JD embraces PNs... not just my own, mind you, but the concept of the PN.
I go to RS from time to time, and I post my PN there when I update it (mainly b/c I posted Chapter 1 there, and I feel like I should finish what I start). I don't post otherwise, mostly b/c I find JD to be superior in terms of feedback and community.
I check in on GH's forums from time to time. But that's about it. I think GH is mostly really good folks, but I got almost no feedback the time or two I posted. It's just not as active.
For other (non-Star Wars) custom work I really enjoy joecustoms.com.
This isn't meant to bash any other site. I think the various communities all do us a service in giving us forums to display our work. I just think that, as a matter of personal taste, the differences are important to understand. The things I like about JD may be things an RS loyalist doesn't like. That's cool with me.