Is this the one in Czech Republic?
I like the idea of this one in that you don't have to go down into the mines. To me, the least comfortable aspect of going into the Heilstollen was the train ride into the mountain. Something about a long slow ride into hot, humid, close quarters with non-english speaking people got to me a little.
I don’t think I can swing Jan 2011, but am seriously thinking about returning to Europe to give this a try. Please do keep us posted on how this goes for you.