First, thank you very much for making Cesium available... It is really cool.
I am having some trouble with Cesium on iOS though. The drillPick functionality will make both Chrome and Safari freeze and or crash almost every time I get more than a few features returned by the function. It happens on both an iPhone 6 and an iPad 2 running iOS 8.4.
Here is a reproducer: http://rikitraki.com/test.html
Just touch the yellow blob near Florida and the browser will freeze.