My experience has been favorable with the customs agents. My understanding is that duty is charged by the bottle, there is a two bottle limit (750 ml bottles), and that you should declare how many bottles total you have in addition to the price. I don't remember the exact duty amount, but it was a ridiculously small amount per bottle (less than $1.00 each) and I was always therefore ready and willing to pay it. I've never brought back more than a case and I've always been waved through - my guess is they don't want to fill out more forms just to collect $5 or $10 from me.