I am experience some basic navigation bugs with the 4.0 API. I have tested this in IE 11, FF (48.01) and Chrome (52.02..) and it behaves the same (when in 2D)
When I zoom in and out when my mouse scroll wheel, then pan, then zoom in and out again with the scroll wheel, there is a tendency for the mouse to get stuck in pan mode. I can duplicate this over and over again. It's a show stopper for me for even using the 4.0 API .
You can test this in the most simple sandbox sample: