Been testing the processor out on my Galaxy Nexus. I rooted it and installed a custom kernel (GLaDOS). Some of my observations.
First off, the kernel control program has options for nearly everything: sound enhancement, screen coloring, vibration control, MPU/Core/GPU adjustments, voltage tables, and more. It's a blast to work with since long pressing any option usually gives you an explanation as to what it does.
First off, core speed adjustments. The core or bus speed is usually involving the RAM. Running at 400 MHz, the program adjusts it up in percentages. Therefore, 110% equals boosting the core speed to 440 MHz. Strangely, I noticed markedly weaker performance.
This is likely due to the fact that the governor for the kernel, Wheatley, is a specially designed version for the phone itself. It works by keeping the processor at its highest frequency set in order to conserve battery. As insane as that sounds, it works. Think of using cruise control on your car to help fuel efficiency and how acceleration reduces it when you start off from a complete stop. The same thing applies here. Forcing the CPU to ramp up, as with OnDemand, the stock governor across most Android phones, wastes energy. I've sampled OnDemand, Wheatley, and Performance (for benchmarking) and have noticed much better response and battery life with Wheatley which is what I maintain for daily use. Core boosting really only seemed to assist benchmarking. Day to day use was impacted negatively. It also was unstable. Approximately one out of four times when I would adjust it, I would suffer a reboot.
MPU adjusting or the stereotypical thought of overclocking is by adjusting the frequency sets for the CPU. My kernel allows for up to 2 GHz, but this varies greatly between chips. My phone can obtain 1.6 GHz before it suffers reboots and freezes. Performance increased across the board from day to day use and benchmarking. Battery life was impacted only slightly and there was obvious heat increases. For maintaining the life of the battery and CPU, I don't think it's good for long term use. The control program also has live OC which allows you to step up the speed in percentages. This can boost performance and speed in a more controlled manner than just jumping to a different frequency set. However, the trade off is reduced stability. My phone may be able to exceed 1.6 GHz, but it will require live OC and voltage increases.
GPU overclocking sets at either 384 or 512 MHz. 384 MHz provides excellent performances boosts with negligible battery impact. 512 MHz also boosted performance without battery impact, but resulted in screen tearing and artifacts. The only way to mitigate this was to boost the core speed. Likely an issue with RAM bottlenecks as the phone wasn't intended to be pushed to this level of speed.
Voltages are controlled in the program and the CPU has a system called Smart Reflex Voltage. This combined with the control program tells me exactly what the optimum voltage is for each frequency set. Adjusting this to the optimum dramatically increased battery life with no stability loss. An amazing idea that really works out. You can adjust even lower to some degree in case the system didn't calibrate correctly, but I wouldn't jump more than 10 at a time for safety. Sometimes when you do reduce it actually re-calibrates it to your value proving it could go just a little lower.
A few other options can boost performance. FSync control reduces I/O operations increasing speed and battery life, but a crash can result in lost data. TCP congestion scheduler settings can boost data speeds. The default is set to westwood, but I found that Reno increased both ping and download speeds. The other two schedulers reduced speeds to a small degree instead.
I haven't done anything with the I/O schedulers. In the past, I've rarely seen much difference in performance. At least on this type of phone. Some earlier phones with weaker processors benefited from a change in scheduler, but with Project Butter, I see no real differences in performance pertaining to this as the only other scheduler is noop which is very similar to sio anyway.
Overall, the kernel and CPU performs admirably. The only real adjustments I found beneficial in the long run were boosting the GPU slightly, undervolting the processor, and TCP adjustments.
Update: I've found that my processor can achieve 1.712 GHz before suffering freezes and reboots. I'm going to be looking into whether underclocking the phone with Wheatley benefits the battery in any way soon.