I don't think I ever used MS Office while that feature (creature? :-) was present, but I think that the main objection to this sort of thing is that it distracts from or obscures the user's work. This can be particularly irritating to a fast and experienced user starting to use a new piece of software
I think in all cases it needs to be kept well clear of the focus, and should never- under any circumstances whatsoever- capture it unbidden.
At the same time, if the user decides to administer the coup de grace to some intrusive UI feature, there should be some intuitive way of re-enabling it... at least on a temporary basis.
MarkMLl