If you are using Yosemite you may have seen jumpy animations. You can especially notice it with slow moving linear animations on non-retina.
This is due to a bug in WebKit2. I have managed to find a workaround/hack and put it in the latest Framer. You can help me testing by choosing File > Update Framer. You can get the old behaviour back by doing Framer.Loop.raf = true.