Hmm. I went to a meet-up for parents and gifted children when dd was little, organised through NAGC. It was actually suggested by dd's nursery - they had been researching options as they had never come across a child quite like her. The group met regularly. I hated it the first time but thought I should persevere, so I went a couple more times. Then decided that it was not for me.
I found the group to be full of pushy parents (believe me, they do exist!) and children with rather poorly developed social skills. When talking to the parents, it was clear that they put their children's poor social skills down to their "giftedness". In some cases, I suspect that ASD was also part of the mix, although this wasn't explicitly stated in my hearing. In other cases, I think the parents were just so focused on their child's academic brilliance that they had forgotten to invest in helping their child to develop good social skills. In a few very sad cases, it actually seemed that the parents were perversely proud of their kids' inability to relate effectively to other children - almost as if that was a badge that proved their inherent superiority. These were the parents who liked to make out that giftedness was a terrible burden.
I don't see it like that. I get that some gifted children may be socially awkward (like some non-gifted children) and I suppose that having a group of socially awkward kids who are all in the same boat does provide a ready-made group of friends who are likely to share some similar interests. So maybe there are some benefits, but these are only really relevant for those children who are both gifted and lacking in social skills. Personally, I feel that it would be far more beneficial to those children if the parents were to invest in building their social skills with ordinary kids in their peer group.
It is worth pointing out that some profoundly gifted children don't have any social difficulties at all - on the contrary, some are lucky enough to be gifted socially as well as academically, with the ability to relate to just about anyone. A more valuable gift than academic intelligence, in my view. These children are likely to have little to gain from a "gifted" group.
The parents at that kind of group are probably best avoided in my view, but again, it depends what you're looking for. If you like to swap notes on how to hothouse your child without appearing to do so how difficult it is to parent a gifted child, then it might be your scene.