I was attempted to try Yosemite OS X beta a few weeks ago in a VM on my Mavericks Mac, using Apple developer account, however I didn’t have time to install in a Virtual Machine, until yesterday, I’ve received an email that Yosemite OS X is released and free to download in App Store, for people who want to upgrade Mavericks to Yosemite OS X.
So I went to open the App Store, and yes, it was there. So I made a full backup of my Mac first, and while backing it up, I google about this new Mac OS.
Found some people want to downgrade or revert back to Mavericks, and it made me downloading the Mavericks.