A lot of North Americans (from Canada, the US, and a few from Mexico even) have purchased the Pandora with little problem. People from all over the world, in fact.
Ok, that's a slight lie: there have been a few problems, notably that they still haven't finished making them all
One guy had some trouble with his credit card, but he was ordering from Russia, so probably not applicable in this case.
Avoid using American Express: as I recall they were jerks over the original payment, refusing to release funds AND refusing to return them (I don't think Craig ever told us what happened with that)
Anywho, no real problems you would need to worry about. Payment is now being done via Google Checkout so you can feel safe that it should be secure. Should you tire of waiting (and you will wait, as I said they haven't finished making them all yet since they're waiting on a new batch of parts) or find you suddenly need the money, refunds are generally issued pretty quickly and without question.