Now having completed my first int'l trip using my BankDirect ATM card, let me add a bit to the above:

1. Guaranty Bank has a 3% int'l ATM service fee that posts as a separate line item from the actual transaction. The actual transaction appears to happen using the actual interbank rate that day.

2. BankDirect with its "no foreign ATM fee" nonetheless seems to post at an exchange rate that's suspiciously almost exactly 1% worse than the actual interbank rate. So, I think in reality, BankDirect (or some upstream provider) is charging 1% on foreign withdrawals, as compared to 3% for Guaranty, but its hidden in the exchange rate. Although getting what I thought was going to be 0% would be best of course, I think that 1% is a reasonable charge.

3. BankDirect attempts to apply the "Up to $2.50 per transaction in network ATM fees will be refunded, up to 4 transactions per month" benefit to foreign withdrawals. It does this by assuming that the withdrawal is in even increments of US$5, and that any partial increment of $5 is the ATM fee. This is almost certainly the same logic used for domestic ATM transactions. So, if you withdraw $303 domestically, it assumes you actually withdrew $300 and that $3 was the ATM fee, and credits you back $2.50 of it. With foreign transactions, an even amount in the foreign currency will almost certainly be an odd amount in USD. For example, if you take out EUR100 and this posts as US$148.69, you get a $2.50 credit, as BankDirect treats it as if you took out US$145 with a $3.69 ATM fee. If you're unlucky to have it work out to something like USD$150.02 because of the exchange rate that day, then you get back $0.02. Kind of an oddball feature, but it works to partially cover the 1% hidden forex fee.