Same here.

I've used the gift/travel cards overseas in South America and in Europe; no problem, they're processed the same way as credit cards (they are, after all, just stored value VISA cards that can only be used at Marriotts.)

The biggest potential problem is the fact that the stored value is denominated in dollars, and if the charge is denominated in another currency one never knows exactly what the exchange rate will be when the charge actually crosses. This is true with regular credit cards as well, but it assumes more importance with a stored value card because there's no easy mechanism for dealing with a charge that exceeds the value left on the card.

So, what I do is this: I check the remaining value on the card, convert that to the local currency (www.oanda.com is your friend if you can't find a Financial Times), subtract 10% from the answer, and ask the desk to charge no more than that amount against that gift/travel card. This pretty much ensures that you won't exceed the value then on the card, and after the charge is processed (usually takes a day or two) you can check the card on-line to see how much remains.

I save the cards with only a few bucks remaining on them and use them up the next time I get to the States. I'm not going to show up at check-out with a handful of cards, though; when I have "odds and ends" to get rid of, I'll take advantage of a slow period sometime before the day I check out and have them credited against my account then.