It seems even 18 is a stretch... now I'm not complaining, because so far I do absolutely love this game. By I just custom bought a brand new computer about a monther a go with a top notch gfx card, a gig of ram, 64 bit AMD athlon processor, the works. Completely designed for the "gaming" stuff, I don't play very many flashy games that require super computers, but I figure, if I have a computer than can run those, I should be able to run just about everything else.
But on Rhy's map with 18 civs, by the late game, just as I'm starting to discover riflemen and such (nearing the end of the industrial era) with 2 of the 18 civs dead and gone I've got the world lagging TERRIBLY. I can't smooth scroll across my map anymore... I try my best not to even look at the other civs or I'll be frozen for a bit of load time, if I zoom out, an even bigger freeze.
and just once, for the first time last night (but too soon for the first time) the game actually randomly quit on my when I was moving a stack of 8 units.
the game is beautiful, and it has the greatest atmosphere of all the civs combined. But I'd honestly give all that up for the same functionality as the other civ. Some games just aren't supposed to be 3D I guess.
They really went nuts with the "less is more" idea.