As a child, I remember wishing more than anything to have my own bedroom (who wants to share with a little sister!?). As I got older and our family moved, I finally got my wish...only to find that having my own bedroom was kind of lonely. My sisters and I would frequently take turns having "sleepovers" in each other's rooms.
My own kids started off sharing a bedroom with a sibling, and as they are getting older (and as we have space in our house) we've been moving them into their own rooms. What works for your family?