Well the way it works for Surface, is that when you update the firmware, a new driver is installed. You can see this in Device Manager Firmware section. Then you are requested to do a reboot. Once you do this, a firmware update is triggered which loads the firmware you just installed to the chips. This last part fails. The system tries to load the drivers in the chip but it fails and after multiple reboots goes into a shutdown state. You can then boot by pressing the power key, and the boot process will proceed but the new firmware is not loaded into the chips. When you finally get into windows you might see "reboot required" in device manager. You can reboot and repeat the process but the load still fails. Finally after 2-3 reboots, in device manager you see:
"This device cannot start. (Code 10)
Indicates a revision number encountered or specified is not one known by the service. It may be a more recent revision than the service is aware of."
This indicates that the new firmware could not be installed. At the same time, the firmware update shows as successful in Windows Update - which is of course bogus. If you boot into the bios by a two finger reboot, you see the old versions of the firmware installed..
No fix or useful suggestion from Microsoft yet.