4.4. Being on VZ the Nexus 5 will do nothing for me. Not big on the lack of SD card anyway or an on-board battery,but I could deal with the other features if it were actually available on VZ for $350. It would get me a phone for literally half the cost of what I'm looking at paying for the N3 Dev edition coming next month.
Wireless printing and other features now being native is pretty nice, plus any increases in smoothness that will be realized.
Having a non exchangeable battery is going to bother a LOT of people dead set on this device. I also came from a Galaxy Nexus and agree that the Note 3 is a better choice (or G2 as I'm using ,)... We'll see I guess. Having the same battery size as the OEM extended Galaxy Nexus battery has, we'll find out just how well the power consumption savings from using a new CPU and GPU (and radios as well) are. Well, anyone getting the N5 can tell me.. I'm quite happy.
I am still happy with my S4 but am intrigued in the N5. Will wait a bit after initial launch to see some reviews and battery life stats but may end up grabbing one.
4.4 for me. I hate to admit it, but I actually like some of the stuff I can do in TouchWiz that you can't do in AOSP. Don't get me wrong, I have XPosed framework on my Note 3 so I can do a few things differently, but still, Samsung finally let me do many of the things I would use an AOSP rom for. All those little software differences now is innovation to me, but from 4.4 and from TouchWiz (Air Command is my big one on the Note 3. Crazy useful.).
Is there any word on if the N5 will even be available for VZW yet??? Have to say I am still disappointed with the N5. If it had been pretty much the same as the G2, as in same screen, button placement and battery size) it would be a winner IMO. So no I have no interest in it. Besides I actually like some of the fluff on the G2. Not as over-powering or obnoxious as Touchwiz. Some of them like the customizable notification toggles, lots of system font choices, lock screen customization, lower button customization and several other things are what would normally make me want to flash a custom ROM. So give me chocolate I guess.