Been visiting Charleston once a year since our daughter started college there in 2008. Just back from third trip, April 2010. Each time there are new restaurants to try. Haven't had a bad experience yet except I'd not return to Sticky Fingers -- not great enough, too touristy. Do Jim & Nick's on King instead for BBQ.
The Palmetto horse carriage tours are a wonderful way to see the city and learn its history.
The shopping along King is fun, if expensive, and the open market, though crowded, can be interesting, especially if you take the time to chat with the vendors. I especially enjoyed Jeff and Lydia Cunningham's GlassArt. They were away in Myrtle Beach over the weekend but we chatted with their relatives, who were staffing their locations.
Have stayed at Marriott Renaissance, Holiday Inn and Best Western King Charles Inn, all with wonderful experiences.
Dined at and enjoyed Hank's Seafood, Jim & Nick's BBQ, Fleet Landing, Wasabi, Tommy Condon's, Joseph's, Muse, Bocci's, TBonz, Noisy Oyster.
Didn't care much for the haunted jail tour -- not scary enough! Other than that, brisk morning walks down to the battery can't be beat!