You see, I'm far from happy with the EU as it is. I don't buy into the Daily Mail hysteria about the EU causing cancer and tarnishing Diana's memory, but I think far too much power is centralised. I'm perfectly happy with the EU as a trading bloc, a free travel area, and even as a group of countries who try and support each other economically, but central control from Brussels doesn't work for small nations. The EU would be dominated by Germany, France, Spain, Italy, and the UK. Ireland's economic success was built on low corporation tax and a knowledge economy, which led to many multinationals locating their European headquarters here. In a gigantic democratic EU superstate, the big countries aren't going to sacrifice their own business in order to benefit Ireland, or Greece, or Estonia, or Portugal.
Large central governments are generally bad for peripheral regions. We've seen that historically even in the UK, with the huge emphasis on London and the South-East from Westminster. Even within Ireland there is a huge bias towards Dublin, as it contains about a third of the Irish population.
And Ireland, and other small nations, could still have a voice in the EU as a political alliance, as opposed to as a massive nation state. Our economy and social policy don't need to be governed by Brussels for that.