I upgrade from the OG Droid to the Galaxy Nexus, and it seems like the battery lasts at least as long, and probably longer, but I don't have any actual data/proof.
My Droid was rooted, but stock ROM, and I was using set CPU to overclock to 800MHz (I believe that was the highest it could go with stock ROM), and some of my apps/games seemed to really take a toll on the battery.
The Galaxy Nexus, with its dual core processor, and more RAM, is able to run those same apps/games more easily, so I've even been able to use Set CPU to underclock it and it still runs fine.
But I also have a charger at home, at work, and in my car, so I'm not always paying attention to how long the charge lasts.