What do fixes for critical security vulnerabilities, improvements to mail delivery, and new FaceTime features have in common? Well, they're all in OS X 10.9.2, which arrived on Tuesday. It's available in the Updates tab of the Mac App Store, and even if you're among those who usually take a wait-and-see approach to system updates, this particular release is worth an expedient installation. 

That's because of the recent SSL vulnerability, which is patched in the 10.9.2 update--that's right, you can let out that breath you've been holding for the last four days since the flaw surfaced. In all likelihood, the gap between fixing the issue in iOS and OS X was so that Apple could get 10.9.2 out the door--though we can debate whether users would have been better served by a faster, smaller patch in advance of the OS X update. (Note that the SSL vulnerability didn't apply to earlier versions of OS X.)

Should critical security vulnerabilities not catch your fancy, you'll be glad to know that Apple's actually rolled out some new features in the latest version of OS X. For one thing, FaceTime audio calls are now supported in OS X, and Apple's also added call waiting, too, meaning we've taken yet another step towards omnipresent VoIP services.

Plus, if you've lamented the inability to block incoming iMessages from particular senders, 10.9.2 is there to help you out with a new feature there as well.

And bug fixes--oh, are there bug fixes. Mail in particular is the recipient of a couple of patches for lingering issues, including improved accuracy in unread counts (just in case you thought "accuracy" was a binary concept), a fix for the problem that prevented Mail from receiving new messages from certain providers (I'll believe it when I see it), and the myriad "general improvements to the stability and compatibility of Mail." Gmail users also get improved compatibility with their Archive mailboxes and labels.

There are plenty of other patches bundled in, including one for audio distortion on some Macs, one for disconnecting VPNs, one for the Mac App Store offering updates for already updated apps, and many, many more. You can see the full list on Apple's support site, or digest the detailed information on the SSL patch and other security fixes in this update (and there are several).

And, finally, for those concerned that Apple has decided to give up patching security vulnerabilities in earlier versions of OS X, the proof is in the pudding: Security Update 2004-001, for the latest versions of Lion and Mountain Lion, arrives alongside 10.9.2, bringing plenty of the same security fixes.