So I got my Nexus 5 today also, but there's no Google Now. Do I have to enable it somewhere? My auto-restore was interrupted so that might have something to do with it. But there's no Google now when i go to the left home screen and when I swipe up from the bottom it just goes to do a search.
I will mention that I did root and unlock it as soon as I got it using Chainfire's method.
EDIT: Nevermind, I got it. I would've thought it was there by default though. I had to long press on the home screen and go to those settings to enable.