If you have qualifying test scores in aptitude and achievement, I would definitely apply. Even if you don't end up using the advocacy services, it will introduce you to a great group of people that "get it" (not an easy thing to find otherwise).
I agree - I took DD to a DYS meet a few weeks ago, DW came along too. It was incredibly calming to sit in a room full of people that got it, had the t-shirt, seen the movie etc. It was wonderful to see DD being able to play chess with people her own age and give her a run for a her money, chat with about stuff that they too got etc.
To chat with adults that had gifted children and compare experiences with them and just hang out and talk about things our children did that would seem like lies or bragging elsewhere.
I felt as one of the Chrysalids must have felt when they met the others from Sealand - people that didn't see them as freaks.