To the extent that you work completely in Java on the server side, mxGraphComponent is supplied as a GWT widget and sync between the server and client is handled automatically.

Similar to what you see in electrical diagrams, I'd like edges that cross to have a small curve in one of the lines to make it easier to follow

create a layout for edges that is similar to the one used by weathermaps to display for exemple the bandwidth use in both ways for a telecom graph

The ability to easily integrate mxGraph in MVC framework with standard interaction between view and controller.

Provide visible gridlines or the ability to set a background image that pans and zooms. Ideally the detail in the visible grid would depend on the scale.

It would be great to be able to do diagram in the context of Jive collaboration platform. Diagraming is a very collaborative excercise, and with the Fortune 500 companies rolling these out, it would present a great opportunity.

It would be a good idea to have some abstractions for easily defining custom nodes with custom editors without having to modify code in different places.