Your Apple users love you for getting them an Xserve with a true AFP service for their file sharing, but your Windows users continually feel that their connections are sluggish. No, don't go migrating all of your Windows data off the Xserve, simply have your Windows users map the network drive that they are trying to access.
I've seen this work at many different sites to speed up Windows XP connections to Mac OS X Server's SMB shares.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20050421162525823