The first update to OS X Mountain Lion, 10.8.1, is now available via the Mac App Store's software updater. As usual, the update contains general tweaks that help boost the stability of the OS. Apple has also highlighted a number of notable fixes, including those that affect Migration Assistant, connecting to an Exchange Server in Mail, and more.

Apple's knowledge base article about 10.8.1 seems to strongly recommend backing up to Time Machine (or some other backup source) before installing the update, though this isn't mentioned in the Mac App Store release notes. Among other things, the update fixes an issue playing audio through a Thunderbolt display, a flaw that prevented iMessages from being sent (I'm looking forward to testing this one), and an issue that came up when connecting to SMB servers "with long names." There's also a fix for a problem that prevented Safari from launching when using a PAC file, as well as one that caused the system to become unresponsive when using Pinyin input.

What isn't mentioned is whether 10.8.1 indeed improves battery life on Apple's notebooks. Users began reporting an apparent reduction in battery life after Mountain Lion was first released in July, prompting us to perform our own tests that seemed to show the same thing. While we previously saw an ~8 hour runtime on a Retina MacBook Pro under Lion, we saw roughly ~5 hours under Mountain Lion.

But one developer with access to 10.8.1 before its public release claimed the update would offer "quite substantial" improvements in battery life, so things may be looking up. We are already beginning our own tests to see whether such claims are true, but let us know in the comments if you end up seeing a significant improvement during your daily use.