Thanks to you all for the comments.
We're still mulling this one over. I can see benefits of both grades. My daughter now says repeatedly that she wants to go to 5K (Kindergarten). We had pretty much decided to keep her in 4k. Aargh. We head to BR for a house hunting trip at the end of next week. We're going to go to the school and discuss the situation with them. She's very mature (socially, too) for her age. As I've said before, I think she could handle it. Something still is keeping me from going forward though. I wish I could place it. We still have a month or so to agonize over it, so if you care to discuss it further, I'll listen.