There is this weird hiccup now, which could pertain the touted data corruption.
My EFI partition contains files with 0 byte size, illegal characters and which are undeletable. I had to rename the "10.12" kext folder, create a new version and copy the needed kexts from my USB bootstick into it. This setup lasts for 1-2 boots or so - then the EFI files become corrupted again. I cannot tell which files do become corrupted, but so far replacing the kexts did it. I consider the EFI parition to be at fault, hence I rance fsck_msdos via single user mode and it yielded an endless stream of errors, which all were fixed. The files, though, are still there.
Tonight I'll use SystemRescueCD to re-check the EFI parition with its tools, try to delete these files and if nothing helps, salvage what is good and reformat the EFI parition and reimage it. This problem only occured while upgrading to 10.12 - or maybe it only became visible.
The HFS+ parition of OS X also shows errors which the normaly fsck did not fix, but which were fixed with/sbin/fsck_hfs -drfy /dev/disk0s2I do hope this does not indicate a corrupted drive.
Similar thing happened to me couple of days ago. Had hwp enabled. Xps went to sleep/hibernation? Then efi corrupted. Tried to rescue it but no luck. Had to format the efi from windows. Then booted the macos partition from usb and reinstalled Clover and efi files