I tried to upgrade yesterday, my machine has Windows 10 Enterprise and Ubuntu 16.04 on two separate disks. The machine rebooted while updating but would get stuck trying to install (once at 19%, the next time at 0%). To recover I had to power off via the power button and when booting into Windows again it would recover to a previous restore point automatically. Ubuntu stayed intact. After checking for the update again Microsoft have removed the option so it no longer appears as an available update, presumably until they either fix it or else as part of a staggered update mechanism.