The Economist has quite a good commentary about EU enlargement and the limited influence of the EU once a country has joined the club:
A common feature in all these tales is the limited leverage of Brussels. It is often said that the EU‘s enlargement policy has been the most potent tool yet devised to entice its neighbours along the road to free-market democracy—far more effective than anything the United States has found to wield over its southern neighbours. But the corollary is a loss of influence after a country actually joins. The pattern of intensive reform to qualify, followed by a let-up in the process once membership is achieved, is too common to be mere happenstance.
There is another big problem with this game: the behaviour of old EU members. Mr Rehn notes that, if one took the worst features of every old EU country, one could easily come up with an amalgam that would barely meet any of the criteria for EU membership. To take just one example often cited by new members, Italy can hardly claim to be free of organised crime.
While reading the article I remembered a very good comment made by Osman Topcagic, the Director of the Directorate for European Integration for Bosnia and Herzegovina whom I met a few weeks ago. He was fully aware of the above mentioned problem and instead emphasized the importance of the enlargement process in itself. Basically he said something along these lines (unfortunately I did not write down the exact words of the statement): It is not important when Bosnia joins the EU, it is important that we reform our country which is the most challenging task ahead of us. The EU helps facilitating this process and therefore we should enjoy the process because this is the time of improvements. And ultimately everyone would like to see improvements.
So, I guess the times are changing. The EU has learned from its mistakes and introduced stricter benchmarks, that can trigger restrictions also after EU accession. At the same time, politicians, especially in the Balkans (Turkey is indeed a different case), see EU accession as a chance to reform the respective countries.
Now only the old EU member states should start thinking about the issue…