We always wait until Christmas morning, but like Bethy, we were always allowed to open one gift on Christmas Eve - usually mine to my brother and his to me. As adults, we've carried on that tradition with our kids.
When I was young, it wasn't unheard of for me to wake the entire house up at 5 am. Of course, that usually meant I'd fall asleep during Christmas Morning mass, something my mother wouldn't tolerate. I do remember the years, when my brother and I were teenagers, that it was my mother waking us up around 9 or 10 am to open gifts. Talk about jaded!
Something my husband does to our kids which his father did to him and his sisters - after waking up, the kids have to stay upstairs while dad goes down to check out if Santa made a visit or not. The poor kids are squirming at the top of the stairs, waiting for the go ahead to come on down. This year it will be to our advantage as we plan to give our kids a hamster, and we want to put it under the tree at the last possible minute (we have a cat).
Lynn