The new Member States will certainly gain most from their new status, but also the current EU Member States, especially those with strong trade links towards the enlargement area as for example Austria, will experience positive effects. Upon entering the European Union, the ten new member states - as I already mentioned - became members of the Economic and Monetary Union.
While they will not yet take part in EMU to the full extent, as they cannot adopt the euro immediately, this certainly is the next step the countries are aiming for.