I'm glad someone wrote this extremely overdue article which would have, in general, been just as accurate two years ago as now. When Yosemite shipped with Safari that worked on only one of my three macs, I knew there was something seriously wrong. Constant bluetooth and RF wireless problems making peripherals hard or impossible to use. iTunes is so shitty, there is not a single redeeming thing about it. 4k support that works, but only sometimes and requires you to plug and replug your monitors till things line up magically. Shutdown/restart haven't worked properly for years and will frequently make the machine hang. Sometimes sleep does so as well, usually at the most inopportune times. The list could go on for quite some time.