onRender currently renders into a temporarily created DIV, and then the first child of that is moved into its place in the container. That's a strange thing to do, inefficient, and also means that you can only create child Components from elements which can be inside a DIV.
It seems that the render performance of the beta release 3.1.1 is still far from the 2.3 performance. If you compare my app here with IE8 you'll see that 2.3 is much faster then 3.1.1 is too slow to accept:
Yes, they say 3.1.1 will address it but I'm not sure if the beta 3.1.1-release already contains all the speed improvements. I hope not because because the current beta release still isn't fast enough for IE.