Yes, it's a lookalike to Harmattan UI, but that is just skin deep. The swipe UI is a pleasure to use but it makes just another smartphone.

The important thing is that it is FOSS all over underneath, that it is possible to go to shell and do quick hacks on the system with tools that already exist there, you can make the device do what you want it to do by just using vi and dbus-send, and just think about it, the device has python preinstalled!

And if that is not enough, it's no brainer to cook up a quick kernel module to change the behaviour of the whole device, or replace the whole kernel if there is something special you need to do.

That is my kind of system. Currently nothing beats it except N900.