I have an FX 5200 256 and it runs even slower than hell.
Haven't run into any rendering problems, though. No black boxes, no interlacing globe. The game runs like it's on a 486, and if I scroll over areas where I have no active units, but I've traded for the terrain detail, the game instantly crashes to desktop. Also it seems to crash to desktop for no apparent reason after every few turns now, regardless of anything else. The game is in the 1400s, epic turn length, huge map. That shouldn't matter, though. On top of the 256mb on the video card, I have another 640mb. When I alt+tab out of the game (which takes 5-10 minutes), the task monitor reports that it's using approximately 500mb of memory at any given time.
It also disturbs me that the game won't accept a resolution below 1024x768. And that there doesn't seem to be any difference in quality or performance if I change the graphics details. Low looks and performs the same as normal or high.
This game is horribly buggy, and the fact that there is nothing in the official support pages, as in literally nothing, as in "there were no results for your search", suggests to me that they really rushed this game out the door for a pre-holiday release.
I didn't buy the game so I could beta test it. If there's no patch in the next 5 days that fixes most of these problems, I'm getting a refund. At the moment it's a pretty looking piece of garbage, and I'd rather play Civ2, since it actually works.
Edit: I forgot to mention. I can confirm that the memory is NOT freed after the crash. I have to do that manually with Cacheman.