See update http://blogs.msdn.com/rido/archive/2010/04/10/trx2html-0-6.aspx
I have released a new version (still in beta) that support Visual Studio 2008 Test Results File Format. It has been really easy, the underlying schema was pretty similar, so I could reuse the whole UI without modification, just 2 hours of XSLT refactorings ;-)
Note that this release only supports the 2008 format.
Next versions will support 2005/2008 in one binary file.