My DD just finished 8th and will be going to HS in the fall. After 6th grade, she skipped straight into 8th. The first month was a little rough. At her middle school, 6th 7th and 8th all wear different colored shirts, so it was obvious the first day of school when she was wearing dark blue and her old classmates were wearing baby blue that something was up.
She ended the year with straight A's including the A in the high school Algebra class she took. She even got the highest GPA in the 8th grade two out of the three times it was given. (Pretty good for a 1500 student middle school).
She was much happier this year, and found friends in her advanced classes to relate to.
However, even with the skip, she didn't need to study. We still haven't managed to challenge her to the point where she has had to develop the study skills she will need in college.
I have loaded down DD's freshman year course schedule with demanding classes (Geometry, Adv Biology, Chemistry, Spanish I & II, etc.) and hope she will have to crack the books this year.
I worry about her starting college a little young, but I also worry that without the challenge, she will start college without study skills.
Good Luck with your skip.