Marionette's Debug mode is useful, if somewhat confusing to use, but it's not as good as a simple 'Watch' node would be. It also involves many more steps (turn on Debug, click on the wire, turn off Debug, change the Node's values, repeat).
Because of the current scale issues (Marionette being 1:1), a node that prints to a text object on a DL sounds like a lot of zooming in and out between the Marionette network and the text object. Plus, if it prints the entire Debug output from a whole Marionette network into one text object, it may get a little confusing about which Node has which value.