This is a very individual, personal decision and no matter what you choose, there will be, most likely, benefits that result and problems that arise down the line. That said, we chose NOT to skip dd ahead. She was already a summer birthday, was already therefore one of the youngest in her Kindergarten class. She had never attended a preschool at all, but either way we would have put her in Kindergarten. More than academics, I think Kindergarten is about learning the school routines, behaviors, and methods. The kids learn about their school, the important people in it, where things are, what is expected of them (NOT academically), etc. When grade-skipping became necessary for us, we knew it. We went to many psychologists first for testing, counseling, etc...and stayed in counseling for 2 yrs afterward. We will probably start back again soon, 5 yrs later. DD went from 2nd to 3rd grade in a small school (everyone knew everyone) midway through the school year. Now, she just turned 12, and is in 8th grade. She is by far the youngest in her grade but most kids don't know it. She is NOT the type of kid who is desperate to fit in. She socially would have had/did have issues regardless of her grade level. She is NOT a follower by any stretch, but is also not skilled in leading, either. So grade-skipping did not CAUSE her social problems, she had those all along. Nobody her age ever gets her sense of humor, is never interested in what she is interested in, and she has always thought that her peers were "silly."
I have rambled forever, here, sorry. If you have any questions, feel free to post them, or PM me. Just know that, in the end, kids who get straight A's are often NOT the most intelligent ones (I was one of the less-gifted straight A students). Often, the most intelligent ones do NOT get the best grades. Most dr's and lawyers IQs are 125-135, whereas a profoundly gifted child (like dd) have IQ's over 160. My dad (definitely a genius, and VERY eccentric) refers to these kids as "Severely gifted."