As another anecdote, I was in one and do recommend it. Yes, the social isolation is a real thing and you have to work harder to meet other kids outside the program. However, I made lasting friendships with others in the program who remain my closest friends today. I think I covered more ground academically and it set me up well to take advanced classes in middle school. Note, this was in a well-funded public school and over 15 years ago so your mileage may vary.