The European Union is now 25 countries strong (or weak if you're a cynic). There's a constant dance of denial that it's not a super state but it sure smells like one. It's got a legal system, a parliment, a budget and soon a constitution.
I don't think it's a bad thing and is just one of the GreatExperiments of the century. If a model of co-operation can be worked out between these countries, then perhaps it can be replicated by other trading blocs and may eventually help to create a better form of world governance. That would be huge progress. In the meantime, it provides a much needed balance to the lone super power in the world.
However, the bickering will be intense and the debates endless. Enlargement just makes it more unweildy. Would have been better to put it off.