"There is also the potential for Fast Startup to get in the way of Windows Updates. While updates will be downloaded for you if you have Automatic Updates enabled, not all of them can be installed without a restart. If you shutdown your computer with Fast Startup enabled, your machine will not perform a complete shutdown, so the installation of updates may not complete. Opt to perform a restart, and this will incorporate a proper shutown and allow updates to be installed -- something to keep in mind if you want to ensure that you keep your copy of Windows 10 fully up to date.
If you're thinking about dual-booting Windows 10 with an older version of Windows or another operating system, you might want to heed How-To Geek's advice:"
"When you shut down a computer with Fast Startup enabled, Windows locks down the Windows hard disk. You won’t be able to access it from other operating systems if you have your computer configured to dual-boot. Even worse, if you boot into another OS and then access or change anything on the hard disk (or partition) that the hibernating Windows installation uses, it can cause corruption. If you're dual booting, it’s best not to use Fast Startup or Hibernation at all."