This is practically a brand-new machine. Purchased a month and a half ago, weeks after the rMacBook Pro refresh. Yosemite is chugging on this thing compared to Mavericks. I'm talking animation lag all over the place. Particularly egregious when I open my Applications stack in my dock, as an example. I have a 27 inch iMac, mid 2010 that is running just as fast on Yosemite as it was on Mavericks. Any thoughts or suggestions?