Yosemite is strange so far in the wide array of experiences, especially considering Apple has so few hardware configurations to target. On my mid-2011 MacBook Pro, it has been perfect - by far the best OS X .0 release ever. Fast and sold. On a 2013 iMac at work, is has had the slow login issues that have been reported. I watched it get rebooted five times and it did something different each time. I guess that is why you don't install .0 releases on a work machine.