I’ve been using MODx on my Windows 2003 Hosting server now for about 1 year now so far no problems
I’ve also got a few customers who use it on my servers aswell.
As the previous posts say mod_rewrite is not part of IIS but you can get ISAPI filters either free or better versions which are paid for and then you can use FURLs.
If you have any problems running on IIS just let me know.
Aaron.