On the subject of the GNex battery life, I am presently running my own little experiment on my GNex. I got fed up with the 2 hours of screen time I was getting on just about any ROM.
So I did a fresh install of Rassaber ( no specific reason for choosing it) and flashed the Rasbean Gapps. With just one app installed - K9 mail set to sync hourly with Yahoo mail and Gmail push mail - I am getting close to 18 hours of battery with 3.5-4 hours screen time (OST).
Subsequently, I installed Facebook, Google Maps , and Google Search ( Google Now). My battery life dropped back to the aforesaid 2 hours screen time. I uninstalled Google Now, and my battery life is back up to 3 hours OST. I plan to run this setup for the next few days, reinstall Google Now and see if anything changes.
To the OP- if you can live with the battery life, the GNex is a great value at $100.
----------
Truthfully, TRUTHFULLY, you are missing very little with Google Now. I have already disabled it as it didn't really seem to add any real value.
I am missing Google Now . I love having all my team scores, my stocks all a swipe away.