Arrives tomorrow for non devs.http://www.macworld.com/article/2456968/apple-os-x-yosemite-public-beta-arrives-thursday.html#tk.twt_jsnellI recommend caution, a FULL backup before you install, and suggest non experts pass.http://www.theverge.com/2014/7/23/5927947/mac-os-x-10-10-yosemite-preview