I have just modified an XML filter for use with OpenOffice based on the odt2wiki.xslt file.
Now you can design tables in OO and export them to NuWiki with the appropriate texts.
Installation: see http://wiki.services.openoffice.org/wiki/Odt2Wiki
Anyone having trouble or not wanting to convert themselves just ask me.
Note: after exporting to the .txt file you can edit the class=altx for different colours.
Use the newer version below!