AFAIK there is one or two ATM's in Athens, not sure if they are still there. One of them was one-way and the other was 2-way.
Apart from that, it's exactly as @thismayor described it. Painfully slow, due to capital controls and also due to a general reluctance to adopt or trust anything new regarding payments and personal finance. Most people are still affraid to use debit/credit cards online.