One data point.
I have had a Nexus 4 for about 18 months. I've had no problems with it so I can recommend it as a solid performer. Runs KitKat official. The screen is not as sharp as newer models.
I've used mine in AU (Optus) and the Western USA (AT&T) on 3G networks with no issues. Saved my arse many times driving with maps navigation voice mode. I expect it will work in Europe too as it supports 900 and 1800 MHz GSM bands.
I get photos and music in/out using gmtp (under Ubuntu 12.04); while Ubuntu 14.04 accesses the phone like a mass storage device under GNOME. Overall pretty good desktop Linux compatibility from what I've tried to do.