If you end up with a delayed flight and need to stay closer to the airport, you may want to consider the brand new "Atlanta Airport Marriott Gateway". We stayed there for a quick overnight layover in September. It isn't a luxury hotel, which we prefer, but it aims to please and the furnishings are all new. Be careful when booking, there are several Marriott-branded hotels in the area, but this one is at 2020 Convention Center Concourse. The hotel may even be on the airport grounds since is connected to the airport via the ATL airport Skytrain, an automated above-ground tram that is quick and not yet a year old.
The room we stayed in was clean and service was above the norm. More than one staff member asked me in the lobby how I liked the hotel and if there was anything they could do to improve our stay. The only hiccups were that the computers were down when we checked out and the restaurant was not good for a late-night meal after arrival - slow service, flat tonic for a gin and tonic, and average food. Skipped breakfast so I can't comment on it.
If you happen to venture into Buckhead, for what it is worth I do not recommend that Westin location after a stay last January. Across the street from the Westin (just down the road from the Buckhead RC) is a beautiful Rosewood property, The Mansion on Peachtree, which is a luxury hotel. We didn't stay there, but ended up enjoying breakfast there one morning; the downside is that it is a good distance from the airport.
A few photos of the ATL Marriott mentioned previously...
(Please excuse the poor quality; I didn't have my real camera and took them planning to write a TA review, which never happened. I'd recommend it for a quick stay in the near future, but I suspect it will show signs of wear and fall into the same category as other mid-level hotels near the airport in the long run.)
Not sure why they put that random piece of fabric over the bed. Those things and shower curtains are pet peeves, but I am meticulous about cleanliness so it may not bother most travelers.