There’s an entire new Storage Management window, located in the System Information app, that provides a suite of tools to help you free up disk space… As you can on iOS, you can tell Siri to make the screen brighter or darker. You can also tell it to turn Wi-Fi on and off, adjust the system volume, put the Mac to sleep, and start the screen saver. Siri also has access to some system information, like the speed of its processor, how much memory it has, the Mac’s serial number, and how much free space remains on the drive.
With macOS Sierra, though, some old Macs have finally fallen by the wayside. Losing compatibility this time: iMacs from mid–2007 through mid–2009, MacBooks from mid–2007 to mid–2009, MacBook Pros from 2007 to 2009, Mac minis from 2009, Mac Pros from 2008 through 2009, and the Xserve. Basically, if you’re running a Mac released in 2010 or later, you can definitely run macOS Sierra.
Hidden feature, indeed.