Um, are we forgetting the fact that the new nexus has and under clocked cpu? Also, on my droid 3 if I over clock it the battery it does drain faster. Im not entirely sure this theory is sound. But I seriously can be =-), technology does change. Im still testing battery drain with the under clock though.
The cpu clocks in the Rezound are asynchronous (separate for each core) and have a minimum preset to (I believe) 384 MHz.
In addition, one of your cpu cores will actually shut down when not in use.
I found no benefit to underclocking my S3 processor to below 200 MHz (with the appropriate custom kernel).
Also, note that SetCPU in Gingerbread tends to eat more battery than it saves when underclocking - you'll find a lot of SetCPU use in your power use profiles.
I expect that very soon (if not already as I type this) you'll find kernel/rom packages that allow you to define min/max clock set points for overclocking - when that day comes, drop SetCPU in favor of that.
Please note -
SetCPU will direct you how to create a file on your sd card that you can flash that will disable SetCPU. Do that. In the event you play around too much, you can send your phone into a bootloop - that flashable "turn-off" file will fix that. You can be one sad panda without it.
By the way - if you like eye candy (and who doesn't? I sure do) try Quick System Info Pro, free in the Market, and go thru settings to show CPU clock speed in your notification pull-down. Then check it from time to time. You'll see that your two core are indeed running at independent speeds and that sometimes, you're only running one of the cpu cores.
Note - not all monitor apps are capable of showing the separate clock speeds of the Qualcomm S3. The rest of the dual cores out there are clocked synchronously - one speed - so some utilities are lagging behind your phone's technology.
Also, note that depending on tasks running, both cores can and will be used to max capacity. There's a lot of nonsense floating around that that's not true until you get ICS. ICS will simply be an upgrade to how tasks are managed for higher efficiency running on a dual core.
Let's see - pics or it didn't happen:
Note - the System Panel Lite not showing a bar level for cpu speed is an idiosyncrasy of it not getting the dual core clocks, as warned previously.
System Tuner, also free in the Market, does show both cpu cores accurately. Note you will find at times that one of the cpu cores will sometimes drop and then show "offline" in place of a clock speed.
Hope this helps!
PS - If/when you do go with a kernel/rom with an overclocking daemon instead of SetCPU, you can easily control it using System Tuner. System Tuner and Quick System Info Pro totally rock.