I would recommend the Holiday Inn Select Airport South via PL. I didn't see a closer airport to the terminals (~1.5mi). Free internet -- wired in room, wifi in lobby. Nice rooms/bed/shower. Restaurant/bar off lobby. Shuttles promptly every 30min starting 5a. That's a soft rule as we got there at :40 past the hour and the front desk requested driver come back for another pickup. Transit time from lobby to terminal ~5min.

I hadn't been to ATL since the Olympics so the following may help others. There is a main security line which appears long, yet run orderly around the morning rush. There is an elite check in line on the left, better approached from the hallway between baggage-claim / ticket-counter and food-court / security.

Specifically with regard to UA529, we left the hotel at 6:40a, got bagels/coffee in the food court, went through security (didn't see the elite line till I got up front, at which point we cut over), and were at the T gate (no underground train ride req'd) by 7:10a. I watched this flight and UA1 for the week approaching my departure. Don't worry about the "close" connection time. It's well coordinated, and stress-free.

I posted a trip report here.