There's a demo for the Xbox 360, I think. Not sure about the PC version.

Well, there IS a demo for the PC version, but it's not quite what you might think it'd be. It's the benchmark program that runs the FFXI engine and allows you to see whether your PC will be able to run XI properly. Check it out: http://www.finalfantasyxionline.com/...asyxi-demo.php