I've stayed at the Renaissance South Park many times over the last four years when I was in the area for business. Flagstones, as others have pointed out, is the hotel bar/restaurant. The food is surprisingly good here. I've mostly had the appetizers like wings or barbecue flatbread-style pizza, but they are all nicely done. A particular standout is the kobe burger- it's expensive at $18 but the taste comes close to justifying the money you lay out for it. The fries that come with it are decent, but if you like burgers this is one you need to try.
The service is hit or miss. I understand that hotel bars can be insanely busy at times, but our server literally disappeared before giving us our check on a visit earlier this week. We had to get the bartender to cash our group out, but she was very apologetic and handled it all with class. The food was worth the hassle, and if you're staying at the hotel you should try it out.