Ok...so... the hotel is ok. It's clean and my one encounter with the front desk staff was positive. However, the hotel is near Pearson... but not so near that you can walk safely. Thus, you are stuck paying $21 for a cab for a 2-minute drive OR you can wait for the shuttle that appears at random (if at all when it's nighttime).
The reason I give this hotel a 1-star is because of the shuttle. The shuttles are simply white vans with basically no space (some sideways seating). They arrive on a whim and when they do arrive the driver will cram many people in as possible India style (in India on the buses they have shovers who push people inside until there is no space whatsoever... Japan too). So, for my shuttle ride the driver put 20+ people into a vehicle the size of a van with all their luggage on the floor... and then sped at breakneck speed towards the airport.
When people started to fall all over each other (no place to hold on) and trip over the luggage (which flew everywhere because it was unrestrained), I demanded he stop the shuttle so people could get out. I got out and walked the rest of the way to the airport. It was dangerous, broke all kinds of Canadian transportation laws, and people got hurt (I fell on some poor lady).
Why not simply invest in a proper shuttle and ditch the van? Marriott can certainly afford it.