My parents declined an offer for me to skip K because I already had friends in my class. I did not enjoy K but that had more to do with my teacher being a mean old lady who taught K for over thirty years and probably never once smiled at a child. I don't think I really learned much academically. I just learned to deal with the routines and boredom of being in school. I am still friends with the girls my parents wanted me to stick with. We now laugh about how horrible our teacher was. For example, she told us before Christmas break that our parents were lying and there really wasn't a Santa. There was also a now infamous class room incident where I was falsely accused and punished (spanking with paddle and no recess). The teacher wouldn't even listen to my side. I remember thinking it was so unfair! Anyway, my friends now joke that she made me what I am today. I am a criminal defense attorney.
So I guess even if you choose Not to accelerate and it goes horribly wrong, your kid might still learn some valuable lessons.