I guess this is relevant here:
In London last month, I used my Visa card quite a bit. I also used my ATM card a couple of times, once for cash and once as a debit card.
The statements are in now...the exchange rate on the Visa was 1.70 to the pound....the cash card (my bank) gave me 1.67 and no exchange fees.
Next time, I think I'll stick with the debit/ATM card!
Something to think about when ordering online, too.