For me, it depends on how close I am to the person. I think that stems from me being just being a more private person than concerns over talking about giftedness. If someone just politely asks "how are the kids?". I will respond with something vague. Mainly because I doubt they really care to hear all the details.
For closer family and friends, I talk openly about it because they know him and know he isn't "normal".
Plus, since a lot of our friends and family were involved in different types of gifted programs as kids, it is nice to get their perspective.
