The problem with (originally) Android-based devices is that their power management is done in a completely non-standard way. It's not that it would not be open, but passing tokenized dead mice through a wormhole
is quite a pain. Will there be enough community interest to actually ever put the power management to a level that can be used by non-Android distributions?
This is where the Neo FreeRunner shines - not only you can install Debian (or Gentoo) on the device, but you can actually use it as your daily phone / GPS device / music player to a similar extent you can use the Openmoko distribution.
It's not just, or it should not just be a "fun hack" to install Debian on your phone - the point should be that you can use your phone with Debian, similar to what you done on your desktop/laptop computer. Of course, there should not be any need to hack the phone before being able to install own programs on it, but there is already the Android dev phone available so that's not the problem with Google phones.