Just installed the Air firmware update...can't say for certain how long ago it was released. FYI I'm on a late 2011 11" i5. I was having problems losing 1.5% to 2% battery per hour in sleep. Last night after the update and with about 98% batt I only slept the machine, rather than shut down as I've been accustomed (no real power loss with full shutdown). This morning I'd only lost about 5% when typically I would've lost at least double that. So it seems perhaps the EFI has addressed this issue, at least in part?