I understand that I can use leapmotion in game with Unity3D.
What I can't see any information on, is if I can use it to actual interact with assets, models etc as I build the game. For example revolving a game object around the x axis or zooming in or out of the view.
Is this possible?
Yes, it is possible, but requires some scripts that nobody has written yet (ASFAIK). Here is a VERY rough example that I worked up today since I've been curious about this question, too.
All it does is move, scale, and rotate a selected game object -- it doesn't try to do this in a good way -- it is a proof of concept only. To make it work you would have to do a sensible conversion of Leap coordinates and rotations to Unity values. To try it, put this script in a folder called "Editor", select a game object in the scene view and hold a key down while moving your hand above your Leap. As I said, none of these movements really work to edit an object, but you can see that it is possible with some sensible logic.