I also started flying out of YVR for the savings - my next flight being 16 June. Since it's an evening flight I'm considering taking the bus or train. Coming back is a different story. My flight (19 July) gets in late so I'll buy a one ticket and fly to SEA. Still worth the savings.
I'm wondering if it would be worth starting a "ride share SEA to YVR" thread? There might just be someone driving up to Canada for lunch that wouldn't mind a travel companion