[john.gersh]

You can certainly do that in the current version. The capability has been there for quite a while.

Your example with a real script in it works as expected in 5.3:

tell application "OmniGraffle Professional 5"
	tell canvas of front window
		set aShape to make new shape at end of graphics with properties {fill color:{51657, 52942, 65535}, origin:{28, 450}, size:{28, 500}, draws shadow:false, thickness:1, draws stroke:true, script:"set the text of self to \"foo\""}
	end tell
end tell