I followed the instructions on the PC support page and went for the three-boot scenario (boot 1: Android, boot 2: Sailfish, boot 3: Debian) and the process ran through to completion. Achieved a partial success: Can boot "normally" into Android; can boot into recovery mode, can boot to Sailfish...
However when I try the boot 3 scenario ("Starting from a switched OFF Gemini, press the Esc (On) key to start the unit until the Gemini vibrates. Once you feel the vibration both Esc (On) key and silver right-end side button are pressed at the same time") I see the planet/tux screen, then it goes dark, then vibrates, then the planet/tux screen, then dark, then vibrates, then... endless repeat.
Haven't had much time in Sailfish (just really checked that I can boot into it), already a few issues... a) The screen starts off in the wrong orientation, but after a few minutes the rotation seems to kick in and it starts to switch... . I have a voice mail, Sailfish recognizes it, but when I try to call to retrieve it says "No Network coverage."