I've been posting my Android questions to Stack Overflow and only recently discovered android.stackexchange.com (which says something about its visibility as I've been posting and answering Android questions for a year).
I'm really happy there is an Android-specific site but it seems redundant to have a dedicated Android site and a plethora of Android tags on Stack Overflow. Even worse, more people post Android questions on Stack Overflow than Android Stack Exchange. Worse still, the only way to maximize a question's visibility is to post on both. Ugh.
As I said I like the Android-specific site, I think there should be only one or the other. Or better integration.