Nice looking Appex site! Just a couple of very quick first comments (using IE on Win8.1):
1)downloading the Mac .pkg or Dreaming Cloud .portfolio just showed the binary file as text in the browser. I guess you need to add MIME types for those extensions to your server.
2)downloading the Windows .exe showed Windows’ nasty big “Windows SmartScreen prevented an unrecognized application from running” screen. I guess you need to use https as well as a signed exe (see my blog for my feelings on this)