Blend offers the ability to toggle the visibility of a Grid's Rows/Columns via the [F9] keyboard shortcut. (also accessible from the Toolbar: Design-->ShowHandles)

This can be useful in instances where the drawn Rows and Columns can 'get in the way' of clearly seeing a design.

As our own shortcut, if we could perhaps target [Ctrl]+[ '] for now.

If we implement this feature, there should also be an ensuing discussion about we currently handle displaying these Grid Definitions. Currently, they show for both the currently-selected Grid, as well as less-prominent/faded Definitions of any parent Grids. This may be an good opportunity to revisit these mechanics, so please bring this up in a meeting when this is implemented, and we can evaluate further.

Please let me know once this is implemented, as I'll have to update our Shortcuts Documentation.