Nice: Windows XP can print over IPv6 to Ubuntu Linux. See the information I've filled out on https://help.ubuntu.com/community/NetworkPrintingFromWinXP
"Windows XP can print over IPv6 to Ubuntu Linux (tested between Windows XP SP3 and Ubuntu Linux 8.10). Make sure both the Windows and Ubuntu have IPv6 connectivity. You should tick "Allow Printing from the Internet" on the Ubuntu machine. Then use the URL (which resolves to IPv6) of the Ubuntu machine as described above."
The result: you can print accross Internet to printers behind NAT-devices.
Arjan's remark: finally we can get rid of faxing machines. ;-)
Question: should we publish the URLs of our IPv6-enabled printer servers here, or will our printer be abused ... ?