I personally thinks it depends on the person, if they feel they look better with their hair up or down, there are a ton of ways to make both fancy and looking great, and I think it also depends on the dress and the way it's cut. Some dresses don't do look the best when you wear your hair up. Others don't when you wear your hair down. Personally I'd stand in the mirror when I picked the dress out and see both ways. Then you have then until the wedding to find pins, clips, ribbions, etc that you want to use.
As getting into that dress on the big day and going. What should I do with my hair? Can really make your heart start pounding especally if your hair has a mind of it's own and doesn't want to behave very well that day. My best friend did that at her own wedding, and with her hair being so long and thick, it took forever to do, and then she change it in the middle, so we had to stall the wedding for 20 minutes to get hair all done. I really felt bad for the groom, who was waiting and probably wondering if we were really having a problem doing her hair, or if his bride got cold feet and the wedding might be called off. We now laugh about it, but at the time it wasn't funny and it was nerve racking to see the time tick by, and have very slow progress on her hair.
Kit