East Germany was an isolated state with its own currency. Its industries were uncompetitive in world terms, but thrived. People had a job. People could afford life's necessities because they were produced within the same economy. East German goods were cheap and could be readily bought by outsiders. The only real problem for East Germany was that it could not afford expensive imports.
Now, the factories of the East have laid off thousands of workers and still cannot produce goods of sufficiently high quality at a competitive price. Large sections of the population struggle to survive on benefits provided at great expense to the state and causing great resentment to those in the West. Nobody feels better off, and this is with a central government that has the will and the capability to direct the redistribution of funds and the rebuilding of the economy. The people of the East have the German mark but cannot earn enough of them to prosper.
What chance then for EMU? Without a strong central government and a merging of vastly differing economies, there is no chance of seeing the long-term stability and planning that give the Germans hope for their future. Are we willing to see millions more unemployed throughout Europe and to pay for this through higher taxes? Do we wish to lose our cheap Mediterranean holiday playgrounds?
I am surprised that so many people seriously believe in monetary union, given the example of Germany. All that pain to give more certainty to traders (try hedging) and more convenience to travellers (use your UK cashcard in European ATMs). For the time being, let the nations of Europe simply try to understand each other more, appreciate each other's cultures, trade more freely, and not get over-ambitious.