I used Christmas cards this year as coming-out cards, too. I sent them to my extended family and in laws, wishing them happy holidays and informing them of my transition and divorce. So far, I've had 2 replies: 1 from my soon-to-be-ex-step-mother-in-law and the other from a cousin. The cousin surprised me as his sense of humor is often macho and somewhat anti-queer.
There weren't any personal messages in with these cards, but they were addressed to Connie, and not David. So, that's something.