The problem isn't so much internationally, I've ordered books from the UK that arrived only one day less quickly than books I mail-order domestically.

Stuff from the US, though, can take a while. The problem isn't so much customs as it is the methods used to handle duty collection. There's a company that does nothing but accept your packages on the US side, pay the duty on your behalf based on the reported value of the contents, cross it, then remail it. Then you get the bill for the duty, plus their fee for covering it, which is often more than the duty itself. It also adds no less than four days and many miles to the shipping.

UPS is nice in that they do their own brokering into Canada, and that seems to be rolled into the shipping fees. Receiver only pays the duty on arrival, if there is any.

But I'm betting customs isn't actually the problem. LeastICouldDo.com (technically SFW, but consider it PG-13) was shipping book orders a few years ago. The orders to the States (from Canada) that went through a certain package class ("Media"?) that US Postal offers arrived a full 4-6 weeks after all other orders arrived, including overseas. Including Australia. Needless to say, LICD doesn't ship books through USPS anymore.

__________________
[Dr. Horrible]___________________________[Penny]
Listen close to everybody's heart________And you believe there's good in everybody's heart
And hear that breaking sound_____________Keep it safe and sound
Hopes and dreams are shattering apart____With hope you can do your part
And crashing to the ground_______________To turn a life around