I've bought 3 cars State side and I don't plan on buying another Canadian vehicle until there is price parity. I brought up a 2005 Toyota Tacoma from Huntington Beach, a 2007 Audi A4 Cabrio from Portland, and a 2006 Honda Pilot from Utah.
Had to pay 6% duty on the Audi, but the others were NA vehicles. No bad experiences at all. I've found this website to be useful:
http://www.importcartocanada.info/