I did a lot of testing and tweaking with the CPU governor and ended up changing several parameters that were causing the CPU to lag by not being able to hit target frequencies fast enough and not staying at full throttle long enough. Perhaps the most interesting is shutting off what appears to be an adaptive powersave_bias. Ondemand seems to work a little differently in JB and I never noticed this until I started testing for JB specific performance tweaks, but the system (probably the kernel) automatically adjusts the powersave_bias like your car's computer adjusting the fuel mixture. If the phone sits and isn't doing much, the powersave_bias ramps up and can hit values as high as 300! That means that if the phone idles for just a few seconds and then you go to open an app, swipe a home screen, or pull up a menu, the system undershoots the target CPU frequency by 30% and you get lag for a second or two until the powersave_bias drops to zero (it takes several seconds to whittle away at the powersave_bias and get it back to zero). Honestly, it's a horrible design. I don't see that it is going to save much power doing that and it's like built-in lag. The solution: set powersave_bias to zero and lock down that entry (read only) so it can't be ramped up. I did a couple other things to improve the rate at which the throttle can be opened and buffered the amount of time it stays at high speed, and you have 2.0.
I've always felt that the JB update was far laggier than ICS. Lag appeared in everything from moving the lock ring when waking the phone, to full second delays opening apps, dropping down menus, and using the back key to get out of an app. So far, all this seems to be solved with 2.0 and we can finally use our phones lag free. This fix should get to the root of the problem (CPU not being responsive enough) without bandaiding it by constantly "pinging" the CPU to keep it at higher speeds. There are some tweaks surfacing (which shall go nameless) that appear to do nothing more than constantly poke at the CPU so that higher frequencies are being used. Hell, if you're going to do that, you might as well just set your governor to "performance": you'd probably get the same battery life and even better performance. Hopefully the performance tweaks in 2.0 will give us the best of both worlds. Maybe I'll wrap this fix up in an app, call it "Dilithium Flux Capacitance Fixer", and sell it on the market.
Mike