I have finished my first version of my program called AvPicFaceXmptagger which takes the Picasa face recognition data for picture files or even a complete directory tree and adds this data as XMP-MP to the JPEG picture files. As an option the people names are added as IPTC tags too. The actual tagging is done using exiftool.
The program is written in .NET 2.0. This program is free for personal and non-commercial use.

So anyone who is interested please check it out and have a try. Please try first with some copies of your pic files - it's the first version of my program and even though I tried hard to avoid any errors I need some people out there to test it. too. Please give me feedback. There is a comment feature on the end of my Wiki page.

Here is the link: http://www.anvo-it.de/wiki/doku.php?id=avpicfacexmptagger:main