Considering one of the main draws of the Macbook Air (for me) is battery life, this was a huge problem.
It took many hours (largely due to my never having done any of this on a Mac before), but yesterday I decided to back up my apps via time machine, format the drive, reinstall Mountain Lion, and restore apps via the backup. (Huge thanks tofor SMS tech support throughout the process.)
Despite the time it took, and some browser syncing frustration that was really an unrelated issue, the whole thing really went swimmingly – remarkably painless, all things considered.
And, best of all, I got up this morning to a machine will the same battery levels (63%) as when I closed the lid at noon yesterday. And I've been working on it, on battery power, for the last three hours, and I still have an estimated five hours of power left. I love this machine.
I'm a little frustrated by the issue with Mavericks, especially considering the OS upgrade was supposed to dramatically increase battery life, but I can live without the Mavericks features for awhile (and the next time I upgrade, I'll have a full Time Machine backup to jump back to, rather than the half-assed thing I had to do this time around. In this situation, I thinkand 's practice of waiting for #.#.1 versions of system upgrades is the way to go.