6 Easy Tips to Speed Up OS X Yosemite on Your Mac
Checking the option to "Reduce transparency" can dramatically speed up animations in OS X Yosemite.
OS X Daily has a great post out about how to speed up OS X Yosemite on older (and newer) Macs. Step 1, "Disable The Eye Candy Transparent Windows & Effects", has done wonders for me. Animations in Mission Control and swiping in full screen mode are much smoother.