I just run at 1024x768.... Interestingly, I was tinkering with my PC last night to solve an overheating problem, and swapped the video output from the DVI socket (with dongle) to the standard VGA output, and I'm now getting a better framerate and zero artefacts - particularly the map was screwed up on certain zoom levels. But it's much better now
(and the PC's nice n cool too).