Build quality is very good, I suspect that the HTC one is higher, but I'm not disappointed. I have the front and back covered in a high quality film and I have a case rather like a bumper but with a clear back you can drop your own photo in. It survives less than delicate handling and sitting in the back of my jersey happily; its predecessor the Nexus 4 took a dive from the top of the lockers in the changing room and the screen is buggered (I actually have it and a screen which I would be open to offers on if you are interested - I can fill you in on why I haven't done the repair).
Screen is precise to use and easy to see, GPS is great. Camera is as good as I'd want from a phone with a chip of that size, one of the reasons I considered the One was the lower pixel count but the N5 is OK. The 360 panorama is a bit of fun if you can be bothered. Again, the One might edge teh N5 on the sound but the N5 sound seems ok to me. No FM Radio, but will stream happily, which is frighteningly practical for both audio and video with 4G. KitKat appears a very strong OS, there's no (maybe not much, I dunno) bloatware so I haven't considered rooting. It is a bit Google immersive though, but I'm happy to sell my soul. It is a little bit disconcerting when you look up a place on Google on your PC, pick up the phone to be told how long it would take you to cycle there.