Google suggests toggling between LAYER_TYPE_NONE & LAYER_TYPE_HARDWARE pre/post animations. This need to actively manage view cache behaviour probably leads to developers being unaware of what to do.
LAYER_TYPE_HARDWARE enables smooth hardware-backed scrolling but glitches badly when the soft keyboard is visible (no resizing/panning of the webview, multiple seconds of delay between key type and text updates inside textfield forms).
LAYER_TYPE_NONE makes scrolling in the webview unbearably stuttering, but at least the soft keyboard becomes responsive, the webview pans correctly to show the field in which you're inputting text, and the key types are instant.
On top of that, there is the problem that you don't have access to keyboard show/dismiss events, so you have to inject javascript code to catch those in every page you plan your webview to display. This is at least the case on the Motorola Xoom and the Acer Iconia tablets running the latest versions of honeycomb.