It must be update Monday at Apple today. No sooner had I updated my iPhone 6 Plus to iOS 8.1.1 than I noticed a little red notification badge on the Mac App Store -- which ended up being the official version of OS X Yosemite 10.10.1 (I've been running the developer beta version for a few days).
As you can see from the notes above, the update improves Wi-Fi reliability, improves mail reliability with certain email service providers and Microsoft Exchange servers, and also makes Back to My Mac remote connections more reliable. It's ready when you are, in the Updates tab of the Mac App Store.
Other notes about the update are available here.