Another advantage of getting off at Viau is that you actually get to see the Stade Olympique, since Viau is not connected to the Stade. (At Pie-IX you walk inside all the way from the Métro to the Stade.)
All the construction and practicality problems aside, the Stade is really impressive to see from the outside. Driving around it at night, it looks like a huge space ship about to take off - I could easily imagine Captain Picard on the bridge…