Haven't had any issues that I can remember while updating to a major Windows version. But it doesn't hurt to make backups before making any major changes to system, (like major updates, changing AV, updating drivers etc) as backups are a part of basic computer hygiene.
Mine won't... I will not be receiving that update. After the 3 second snap shot announcement, I put 10 and 11 on hold, no more major updates, just security fixes.