However, there are some real benefits to DD to being in the full-day gifted program. She's very happy socially, and has lost the unattractive vibe of "Why is everyone else so...slow?" that she was developing. I sometimes wonder about the long-term consequences of being segregated in this way, though.
You mean as opposed to the recognition that you stand astride the world like a colossus and a supreme confidence in your own opinion to the exclusion of all those opinions outside of your own?
(I'm betting that I'm the only person who's ever yelled out in their sleep "The only opinion I care about is my own!" I woke up everybody in the house that time, too. Fortunately, I'm always able to go right back to sleep.)