I guess the problem also exist with the Visio Converter available at
http://www.conceptdraw.com/en/visio/ but at least it partly allows mass conversion.
Or am I mistaken that VSS files are simply renamed VSD files? I'd also like to convert a few simple stencils to Visio, sadly the Online Conversion service seems to take a while until the file is sent. Anyone experience with this or other services?