We bought a FP1U some three years ago. Though its spec was quite higher than we required, we went for it because of the basic underlying idea of recycling and avoiding unnecessary waste to the planet.
We have been very happy with it until a few days ago, when the battery bloated. Then I started looking for a replacement and, to my despair, I could not. I have read a lot, including the post on using batteries intended for other mobiles. I am unsure about this option - the only one we seem to have now - despite the positive comments of brave FP1 users who risked it. Thanks to them all for sharing their experience 
It is disappointing having a mobile intended to be ecological and, for a small maintenance as it used to be a battery replacement, having to throw the whole device away. However, I am grateful to FairPhone for the idea and for their support, but I think the moment has come when the “markets” make it not feasible to follow this way. It seems the trend now is to manufacture mobiles without a removable battery so the battery manufacturers will be doing something else.
The idea of a sustainable mobile is still good. We need to go after it, but it seems we cannot do it relying on providers who do not care as much about the planet.