In my recent post about the rMBP vs the 2012 MBA, I posted how I decided to go with the 2012 MBA for now. So far I'm loving the battery life on the new MBA, I installed Mountain Lion and I'm getting right around 8 to 8.5 hours with web surfing, email, iPhoto, and other light to moderate applications running. I know some have problems with battery life on Mountain Lion but so far it has been very good on the 2012 MBA and been a pleasant surprise. Only negative is I liked the old magsafe adaptor better.