Here's my take on the gnex battery...it absolutely sux...HARD. I just put up with it because every other aspect of the phone is great. (well maybe not the camera). I have the 2100mah extended and when I first got it, it was noticeably better, nowdays not so much. It seems to have lost some juice. I can't tell it from the reg 1850 batt.
I been on many many roms and kernels and have adjusted governors, lowered clockspeed and just tried lots of things to try and get better life. Guess what....I find all the things I do, the difference is negligible. Like Lum said above, batt is determined mostly by your usage patterns. the problem lies is how do you compare different batt cycles to one another? It is impossible to use the battery the same for 2 cycles.
So, bottom line is just find someway to live with it (spare batts and chargers) because this phone is still one awesome piece of work.
Also, I been really considering getting one of them Hyperion or Seidio mega 3800mah suckers. It'll make the phone super fat but might be worth it. Seen the Hyperion on ebay for $19 the other day.