Received a WPDM Registration Key by email - no reference to beta testing, but I logged in to the www.touchxperience.com forum, (eventually) found the 1.4 software, downloaded it, and installed it (guesswork - no instructions provided).
I have got it to work, which is very good news.
There are lots of undocumented things you have to do to make it work and keep it working (e.g. none of the connectivity works unless the automatically installed TouchXperience app is active on the 'phone).
The application clearly has absolutely no knowledge of the existence, let alone the internal storage, of any Marketplace app (which doesn't surprise me at all, but which means it's pretty useless as a backup engine).
More details when I have time (and when I have checked whether I'm allowed to give specifics of the 1.4 version yet, since I am on a private beta).