I'm at the point now where I won't get a mobile 'smart' device unless it's a Nexus. I might consider a GPE device, but what's the point when there are Nexus devices that are just as good, if not better, at a lower price?
Essentially, in my opinion Nexus devices are real Android and everything else is bloat. Android (Nexus) devices are hugely customizable, even without rooting them, so if you want more functionality in some kind of way: There's an app for that.
It might take a little time learning how to set up your Nexus 5 how you want it, but that can be fun in and of itself too, if you're into that sort of thing like I am, tinkering around with stuff.
The Nexus 5 is a great device and is on the forefront/cutting edge of 'smart' device capability and technology still in most ways, and is more powerful than most other things out there at the present (all iPhones included).
Not to be rude, but why anyone would waste money on devices that are less capable and cost significantly more is beyond me. Although, to be fair, Nexus devices aren't advertised nearly as heavily as the main competitors out there. I rather like it that way; It's almost like a secret club for people in the know.
Beyond that, all that's left really are just fit and finish personal preferences.
The Nexus 5 isn't perfect though, so to be fair: It doesn't have expandable internal memory, nor an easily replaceable (user serviceable) battery. The on-board speaker isn't that great either. But, it's a phone speaker. I would hope people aren't expecting too much from a phone speaker. If you want high quality audio, get some good speakers or headphones, and maybe an equalizer app.
Despite some of the ongoing criticism, the camera on the Nexus 5 takes great pictures. Just use HDR+ and tap on the menu to navigate it instead of trying that silly menu drag interface that everyone seems to try fumbling with when they don't have to. A friend of mine is the proud owner of a golden iPhone 5S, but we took side by side pictures, and we both agree the Nexus 5 takes much better pictures. It was actually pretty surprising, after all the negativity out there directed at the Nexus 5's camera. Maybe people/reviews just never learned how to use it, nor used it after the 4.4.2 update.
Anyway, if you do decide to pick up a Nexus 5, feel free to ask me and others in this forum for pointers and any questions you might have about it.