Update instances of stencil objects
 

Anyone know of a solution or work around for this?

[B]I would like to be able to update objects in a stencil and have the changes reflect/cascade down to the instances level.[/B]

I work with very large scale applications and am always having to update wireframes at the stencil level (example: header or navigation elements on a website which are subject to change in early stages of a project).

Modifying the stencil won't affect shapes used from it. But there is a way to update all the objects of a certain type at once.
The canvas inspector has a selection tab. This will show you all the different types of objects in your document. For example, it might say you have 8 green circles and 4 blue squares. If you click on the green circle icon, it will select all the green circles in your document. Then you can use the other inspectors to adjust their properties (color, dimensions, line weight, etc.) Hope this helps.