Based on our experience, I would probably recommend an early entrance to K over skipping directly into first. For us K was a half day; there were lots of fun activities and the teacher had a fair amount of flexibility.
In first, the teachers felt so much pressure to get every kid reading by the end of the year (because of the nature of our demographic, most weren't reading coming out of K), there really wasn't much time to try to adapt the curriculum to a more advanced kid. It was all about remediation for the kids who were having trouble, with very little flexibility because the teacher was stretched too thin trying to meet strict state guidelines for reading. I just think with the right teacher, K can provide a child with a smooth transition into school life. I think, at least at our district, to have dumped DS directly into first would have really turned him off to school.
Obviously, so much depends on the teacher, the kid, the school, the district etc. This is just my feeling based on my one kid.
