Scott, I, and others are building a Cesium App for 5 - 10 year olds where the camera can either follow an object (same as double clicking on something in Cesium Viewer now) or free roam (our default camera).
We are designing a navigation widget so users can control the camera with just the left mouse button like we see in most maps and globes. At first, I was hoping that this widget would be a complete solution for Cesium in general. However, given our novice users and that we want to match Bing Maps to some extent since we are using Bing for 2D and non-WebGL platforms, I’ve made some simplifications compared to full-featured controls we see in Google Earth for example.
In particular, this control can’t tilt and orient at the same time or control the zoom or tilt speed. This is fine for our app that needs to provide the simplest possible interface and most obvious discoverability. Later, for Cesium in general, we may also be interested in rubber-band zoom and selecting home/object views.
I attached a paper and pencil mockup. I think this is a reasonable start for navigation, and perhaps the full-featured control will even have novice and expert modes.