The switch will be more apparent overseas than in the United States, since McDonald's only serves Heinz ketchup in two domestic markets - Pittsburgh and Minneapolis
Last time I was in a McDonald's, it was Heinz. That's Ontario though.
I'm more worried that Heinz will change their recipe to cut costs, but this does make me less tempted to go to McDonald's. Restaurants that serve inferior ketchup are crap. The worst are the ones that hide it. They'll have Heinz bottles on the tables, but when you taste it, it's not Heinz. They think we won't notice, but we do!