The money is not withdrawn from your checking account in real time as it would be if you used an ATM card. Instead, American Express advances you the funds, adds 3% plus ATM operator's fee, and generates a EFT debit to your checking account. I expect the funds would be withdrawn within two buiness days, but I have never tried the service. The limit is $10,000 per 30 day period.

As mentioned, the alternative is to go to an American Express Travel Service office and use a personal check. The same $10,000 limit applies, $500 in currency, the balance in travelers cheques.

For someone who does not carry an ATM card or checkbook when travelling it's a useful fallback in the event of emergency.