Got a platinum upgrade to a corner king suite on the 14th floor for a 1-night stay.
Overall, as suggested above, this property is much nicer than an average Sheraton. Nice wood floors, "old-time" ambience. The building's footprint is actually pretty small, which means the two restaurants are (respectively) in the basement and on the mezzanine level. Reception, Sheraton Link area, and two small bars (one inside an old bank vault!) take up the main level. The small footprint also means that there are only a handful of rooms on each floor, which I thought made for a somewhat cozy feel. It also means the rooms are not especially spacious.
I agree with a previous comment that this could almost have been a Luxury Collection property, but I'd think LC would at least have wanted to see more space available. As it is, the overall feel of the place is actually a little more like a Westin to me than a Sheraton.
The club lounge was "undergoing renovation." I went up to the club level and found the room labeled "club lounge," and it didn't seem to be under renovation at all, but was set up as a meeting room. It seems a bit small for a club lounge. Since the lounge was not available I got a free breakfast coupon. The breakfast buffet was quite nice, and ended up being a much better value than a free evening snack and the typical lounge breakfast.
My suite had a flat screen TV, a coffee table, a sofa, and a lamp in the living room, and essentially nothing else, as there was not room for more. This was plenty, though, although I definitely missed the comfort of a pillow or 2 on the sofa. I suppose I could've used one from the bed. The bedroom was smallish but adequate, and had a second flat-panel TV. The bathroom was not huge, but nice (no tub-shower only), and included a third flat-panel TV, which I found a nice touch. Windows in the suite added a nice, airy feel to the rooms. There were two free bottles of water, but no bathrobe. I was surprised and disappointed to find that there was no folding luggage "valet" in the closet, though I find one in every other US SPG property I've been to. So I had to put my bag on the floor.
The hotel offered shuttle service to take me to dinner (I chose Gervais & Vine, which I recommend - try the Moroccan Pork with Gorgonzola fondue), and shuttle service was prompt and friendly. Parking is valet-only, at $18/night, which seems a bit steep in Columbia, even though it is a downtown property. The manager told me I could probably find a spot on the street for free after about 6 pm, but I didn't bother trying that option.
I mentioned above that I could have equally chosen the Westin Poinsett in Greenville, SC for this stay. In general, I like the room quality at the Sheraton Columbia better than the suites I've had in Greenville, though in Greenville it's nice to have a little more space. Though I had a very good meal in Columbia, I vastly prefer the appeal of Greenville's downtown and dining options to those of Columbia. Given a similar choice in the future, price would play a part in the decision. If prices were comparable, it might come down to the weather. In weather that would reward an evening stroll, Greenville's downtown would draw me there. If it were too hot or too cold to spend much time outside, I might pick Columbia.