Obviously, the best rom has a supercharger under the hood!
Just kidding of course.
But about battery calibration... I actually came up with a pretty nifty no battery boot calibration....
xda-developers - View Single Post - Battery Calibration
My freaky Milestone boots without a battery and it turns out that droids do too
Basically, charge to 100%, delete batterystats.bin, reboot normally, pop out the battery before the m logo and pop it in when you see the lock screen... then you can monitor the charge (I like battery monitor widget) and use the phone normally.