I spent this past Christmas night at the Westin ATL. As airport hotels go, I would recommend it. As a Gold, I was given a nice room on the top floor and the front desk agent made a point to remind me that yes, the lounge was indeed open on Christmas night.

Shuttles were plentiful - didn't have to wait more than about 3 minutes going either direction. Ride to the airport is about 5 minutes.

If you have an option to stay downtown, well, I'd always take anything over a dreary airport hotel. But if you gotta stay right by ATL, this is about as pleasant as an airport hotel can be.