For those interested, I just posted an article to my blog detailing how to use Espionage together with Dropbox. I know there's an article about this somewhere on the Tao Effect, but I wanted to go into more detail and present the process in the context of a use case that probably will appeal to a lot of people:
http://www.dafacto.com/2014/02/09/how-to-share-confidential-documents-using-dropbox-and-espionage-for-mac/
http://www.dafacto.com/2014/02/09/how-to-share-confidential-documents-using-dropbox-and-espionage-for-mac/