Thanks for the tips. In a Pavlovian way, I've been trained to expect the worst of Canadian customs/immigration (half an hour of questioning because on arrival in YVR I couldn't name any local tourist attractions) -- maybe I should try it sometime and hope for the best. The possible delays at the crossing, especially if I'd be driving back to make a flight, do make the option less appealing.

Thanks also for the tip on the "truck crossing" -- this works in both directions?