It seems the Euro was set up to fail or at least with easily implemented mechanisms to carve out remember quickly.
I would be getting my "money" out of EURO or at least Greek Euros ASAP.
1 euro = 1 euro no matter what country minted it.
The only time where this is not true, is for collectors, as some people like to have a coin from every country, so they might pay a small premium for rare coins that are no longer in use (mostly 1 and 2 eurocent coins that are not even minted anymore in some countries).