The preview page outlines something called 'Optimised Storage', on one part it seems like a good idea, but one part also has me concerned. "Storage space maxed out? No problem. macOS Sierra can help make more room by automatically storing rarely used files in the cloud and keeping them available on demand." I DO NOT WANT MY FILES UPLOADED RANDOMLY. In part because they are MY FILES, and in part because I also have a horrible internet connection that cannot handle the requisite sync load. Also, 'Your Desktop and Documents folder. Accessible on all your devices.' Disabling this immediately due to both the same points. Other than these two problem 'features' macOS Sierra looks like it'll be an improvement. Siri looks like it won't be in the way, so I'll take a wait and see approach with that. Plus, the name change was a long time coming, 10.10 and 10.11 made no sense being called 'OS X' to me.