The bad news is that Windows 10 build 14279 for the fast ring causes the Surface Book, Surface Pro 3 and Surface Pro 4 to freeze. Once that happens, you are unable to use the Type Cover keyboard, the trackpad, or the touchscreen. Microsoft does have a workaround. They suggest holding the power button down to force a hard-reboot.
If you own the Surface Book, Surface Pro 3 and Surface Pro 4 and are affected by this freezing issue, know that Microsoft is aware of the problem and is investigating it. Hopefully, a fix will be pushed out in the not too distant future.
Microsoft Surface Pro 4
source: Microsoft via MSPoweruser