We too sailed on Galaxy, in 2005 and from Charleston (five hour drive for us). It was our first experience of Celebrity, and we loved everything about it. We've sailed Celebrity ever since.
My concern is that Mercury (and Galaxy) have gotten a bit worn around the edges since then, as they approach the end of their service with Celebrity.
A Captain's Club rep. told me that Mercury was OK when she took it a year or so ago, with new carpeting, bedding, etc. I hope you find it so.