Except for the installation process SailfishX feels great.

New ambient looks very good, it's smooth, has lots of mem (no swap!), virtual keyboard sounds and vibration work as they should and there is Android support. Me happy.

I might still switch to Compact when one emerges because of size (and I don't need Android support _that_ much).

Regarding unlocking process of Xperia X:
As always has been the case in the past, even Sony's own instructions claim that one has to enable USB debugging mode under Developer Settings in Android. However, unlocking does not work with that; you have to select OEM unlocking.