We're getting a whole lot of use out of it. This is the first time I've used Dragon in about 7 years or so. The last time was the Dwarf article that came out after 3e's release.
I have used the rituals, personally, as I'm playing an Eladrin Wizard right now.
My friend, playing a Warforged, has been getting much use out of the Ecology article, as has our current Dragonborn player.
The guy currently DMing our game is going to be sending us into Vor Kragal in a couple levels, and while we were crossing the desert to find the current town we're helping out, he sprinkled in some of the Dark Sun threats.