Love YEd -fantastic product.
I would love a format painter to allow easy transfer of colours, linestyle, linecolor etc from one node or edge to others.
I often use flow charts to model sequential and branching within applications (or part therof) but color the nodes differently where different classes and methods within those classes are performing different parts of the overall application. I find this essential as I find sequence diagrams do not represent branching in the flow of the application well or in a manner which is useful to me.
It is fairly tedious to manually change the colors of the nodes and being able to copy either all graphical properties or selected graphical properties from one node to another similar to the format painter in microsoft products. I have achieved it by copying an existing node and relabelling it. Also while the ability to select multiple nodes (or edges) and then set the properties of the selected group does help, it is not as natural as being able to drag and drop the graphical properties.