I think it is very difficult to predict, as it depends so much on the specific child. But I think you knew that...
My own experience was largely positive. I also just missed the cutoff, and was entered early, skipped once at third grade, again at ninth, and left high school a year before graduation to enroll in the university. So four nominal skips (although the early entry to K was negligible). In the grades that encompass third through sixth, I was in various forms of gifted programming. In junior and senior high, I was not, but had a custom schedule, with additional acceleration in core academic subjects.
Factors that I think helped to moderate the peer social impacts include having HG+ siblings close in age, a community with a high performing peer group outside of school, and extracurricular interests that were not as affected by age/size (I was not an athlete). I am also rather small of stature, which may have steered me away from sports, irrespective of grade skips.
Regrets? Maybe a few awkward pre/early adolescent romantic encounters, which, at the time, I thought were awkward because of my age difference, but in retrospect, were just awkward because of my age, period.
Among my children, I have an early adolescent who skipped K and 4th, who appeared to be largely happy with the course of things while still in a b&m school. The one comment I have heard is a dislike for being treated (in a warm, cuddly, class pet kind of way) like a baby by classmates--although they consistently respected the academic aspects. This particular child is highly social. The others have been predominantly or solely homeschooled, so it hasn't come up as much.
