I would advice NOT traveling with Quickshuttle alias Quickcoach when wanting to circulate between Vancouver/Seattle. The pick-up shuttle did not show up at my hotel, I got no apologies, just a blunt "I did not come", "but you made it, anyhow"... I had to pay a 6 Canadian dollars for the taxi to get to the bus. The staff was not very service-minded and totally careless whether I made my bus or not.
After all, my aim was to get to Seattle airport and wanted to catch my flight that same day. For the price you pay for and the time it takes, you can as well rent a car, drive it by yourself, stopping, if you so like. Border-crossing is not any more difficult, and if there are more than one passenger, it will be cheaper.
No wonder the bus operator is not a member of Vancouver tourist board, as they obviously have no desire to get feedback.