I'm enjoying reading about how everyone has made the whole grade/subject skips/nonskips work in their families, with their kiddos. There are definitely many factors to consider.
I just wanted to throw out my personal experience re: going to college early or graduating high school early (although technically I didn't graduate early). I was the youngest in my class with an end of August birthday, but not grade-skipped. I do not claim to know what flavor of gifted I am, but I was globally gifted in school. If I had heard of grade skipping, I would have begged for it. When the post-secondary enrollment program began (i.e., go to college while still in high school), I jumped at the opportunity and went full-time to the local university instead of my senior year of high school, getting credit for both. So, I started college at just-turned 17 (just like kids who graduated high school at 16), and I would have started the year before if that had been an option. I loved it. Although of course we worry as parents about sending our young kids to college (and of course younger ages are being discussed here), at a point it just is a natural progression to the kid. At least it was in my experience.