I've known Slovenia since it was part of the former Yugoslavia, I was there again recently and they are very nice people, but there are only 2 million of them and they have run up massive debts to the EU (check out their economy).
In my experience the problem is that though they have massively increased their standard of living and the country's infrastructure since joining the EU, the people seem to live still under the old communist ethos; several people doing a job that could be done by one etc. and a noticeable lack of entrepreneurship.