Hi Marc, the new patch here: http://moi3d.com/forum/index.php?webtag=MOI&msg=1013.24
now enables the Alt key override for temporarily disabling snapping.

The only thing is I'm not sure about disabling Grid Snap along with Straight Snap and Object Snap. It seems like it might be a good idea to leave Grid snap on if it was enabled, that way you would be able to use Alt+click as a shortcut for kind of reaching through objects and getting to the grid.

- Michael