BMEcat (a standardised XML format) is Europe’s most important data exchange format for ecommerce, tons of major companies are using it over here -> see http://www.bmecat.org/English/index.asp? (Version 1.2, the new version 2005 is hardly used by anyone because it is not compatible with older versions)
Many of us think that Meganto should have a standard BMEcat import. Will it come soon?