If you have an Apple MacBook Air and you have not yet received this update, you should get it. In fact, I'll take a moment to step aside and push really hard about performing regular updates to your Apple systems. By default, your Mac should check the mothership for updates automatically. If you have turned this off, go and turn it back on. Updates to the Mac are very important, and I'm not just drinking to kool-aid.
If you like, you may also download it directly from Apple at this link. The fix is for various power management functions as well as support for new battery modules for the MacBook Air. Enjoy!