Midtown Atlanta. I was Cingular/ATT prior to switching to Sprint on EVO launch day. Online Sprint maps show strongest signal for both 3G and 4G in this area. I've found these to be a lie.
Coverage is generally worse than on ATT (perhaps unsurprising: ATT has major offices in Atlanta). I don't think I've ever seen more than 3 bars of 6 on my EVO. Signal is weak enough that I have to pay attention to how I'm orienting my body during a call so that it doesn't drop. More dropped calls than when I was on ATT.
4G service is OK outdoors, but absolutely non-existent indoors. Within two steps through a door into a building, I've lost the 4G signal. It literally only penetrates about 3 feet into buildings. (Note that these are large buildings with concrete & rebar structures, which pose obvious difficulties for any radio signals. 4G is particularly bad, though).