This issue must have affected limited models as I have seen no real impact to my battery life running Mountain Lion with my MacBook Air.
It's interesting to see that Apple's largest strength (one hardware platform running one OS that they control) still doesn't mean that everything works as expected. I wonder if ML, being 100% 64-bit code from the Kernel up, increased power usage on older Macs that were designed in the Leopard/Snow Leopard days?