OS X is now macOS, and macOS 10.12 shipped yesterday. You may well be seeing prompts to download and install from the App Store. At the moment I suggest waiting a few weeks to let the initial bugs be found by others, and for the inevitable .1 release to come out.

Third party software is still being updated for Sierra; while developers have had access to beta versions there are always glitches with the actual release. For example, Mathematica is known to have issues with some localisations.

Symantec has support for Sierra in their latest Mac release and I am working to get a copy of that uploaded to Managed Software Centre ASAP. Other software updates will be uploaded when they’re available!