Hey,

I worked on the context menus for the webworks platform and found a cool trick to improve animation performance for context menu. For smoother transitions when pulling in and out as well as the unfolding actions, I utilized a technique to force the device to perform hardware acceleration when performing animations. To do this you just need to make the CSS use some sort of 3D or hardware accelerating property. I use this for our CSS stuff:

-webkit-backface-visibility: hidden;
-webkit-perspective: 1000;

I found it from here:

http://stackoverflow.com/questions/10014461/why-does-enabling-hardware-acceleration-in-css3-slow-down-performance

I found it made our animations much smoother and fele more like native.