It's not the rom giving everybody false readings of their battery, it's the battery itself.
Lithium-ion batteries have an internal fuel gauge that can become inaccurate over time due to charging the battery over and over before it ever goes dead. So the most basic way to reset the fuel gauge is let it drain completely dead until your phone shuts off, then recharge it completely full without taking it off the charger and TADA your fuel gauge is accurate.
The only reason everyone is noticing their fuel gauge out of calibration all of a sudden, is because this rom is set to read the fuel gauge in 1 percent increments, when before it was set to 10/5 percent increments which I'm pretty sure it just rounds to the nearest percentage, so nobody would of ever noticed.
So when your phone is fully charged but the gauge says 97, or whatever it may be, is because the battery itself is actually fully charged but the internal fuel gauge is out of calibration.
Hope this helps:-)
Sent from my STEELDROID3 2.0