Not quite what you're looking for, but I'm playing on a large earth map, well into the late game, on my 2009 27" i7 with the 4850. At native resolution with some of the game settings turned up, playing via Win7 64bit.
No noticeable graphics issues, at least not enough to get me worried. Scrolling is smooth. From what I can tell, any lag I experience is between turns while the AI is making its moves.