Upgrading to .0 release of a new OS is not something a professional that relies on a working system should be doing.
You're right, that's why I have all my work on multiple backups, and another machine (iMac) running Yosemite that I can rely on just in case. But you would think that a major update to a very popular OS, which has been apparently beta-tested for months, would have less significant bugs. Just my 2c