I didn’t read all the previous replies, but here are my experiences so far:
It’s pretty powerful, but also doesn’t use much battery, I even let it running in regular day mode (internet connected etc.) at night (uses about 2% per hour that way).
I almost never have performance issues, which is a great relief from my previous phone, where absolutely everything lagged at the end.
It also has a 1080p resolution, which is awesome. Whenever I now use my old phone, everything appears huge.
It has no NFC, but the NFC connection of my Bluetooth headphones never worked properly anyway, so I don’t mind that. And I put my EC card into it (there’s just about enough empty space inside) and can now use it to pay anyway.
I rarely listen to music using the speakers. The quality of them is alright, but not good. If you want quality, I don’t recommend phone speakers anyway.
Bluetooth headphones cause no problems, other than the usual Bluetooth hassle of having to manually select it again if they were previously connected to a different device.
The headphone slot also works well and using it to use the phone as a microphone for a PC actually gives me the best audio quality of all microphones that I own.
Now to the problems: I have a relatively new Fairphone 2, which contains a camera module that has problems with newer Android versions. After I installed Fairphone Open (which is ridiculously easy to do, compared to my previous two phones), I had such a new Android version, I think it was Android 7. It also had some other problems, like GBoard crashing whenever I try to open the settings, rebooting when I try to shut it down and a few other things. I solved most of them by installing LineageOS (Android 8.1 at the time, now Android 9). The only problem left now is that the main camera doesn’t work most of the time, so I have to photograph with the front camera, that’s quite annoying. But I admit, I haven’t reported the bug yet and I don’t know if someone else has.
If you use XPosed, you can’t disable it with the key combination while the phone boots. The solution is to put the disabler on the SD card ahead of time and just flashing that with the recovery when you have a bootloop. I installed 14 mods, most of them not even made for this Android version, and only had one bootloop so far. If you just install the standard stuff like GravityBox or Scoop, you should have no problems like that.