Have you considered the Renaissance? It's a very nice Marriott property.
If you want to stay in Charleston, I would suggest the Embassy Suites. It's a nice location, but parking is limited and the rooms can be a bit dark. Additionally, there is a nice Embassy Suites near the airport at the convention center. It is actually in North Charleston.
There is a Hilton across the river in Mt Plesant, but I've heard mixed reviews of it; especially regarding upkeep. There's a Doubletre in Charleston and a Garden Inn near the airport, but I don't know anything about them.
[This message has been edited by BillMorrow (edited Dec 10, 2003).]