The conflict over who would head the new European Central Bank spoiled what was meant to be a celebratory weekend for Europe's leaders. Mr Ahern said it was ironic that at an historic moment the fight was over one of Europe's better-paid jobs. It will be some time before the implications of the damaging row clarify.
The summit marked the effective beginning of the single currency, with the EU leaders approving membership for 11 states and deciding rates at which the currencies should be locked. While the euro does not formally come into existence until January 1st, the political decisions are made.
Indeed, it will even be possible for big investors to buy and sell the new currency in a "grey" or unofficial market from today, where they will enter contracts to switch their current foreign exchange holdings into the new currency next January.
Ironically, Britain, where the single currency is so divisive, was in the president's seat for the occasion. The British Chancellor, Mr Gordon Brown, hailed this momentous decision and forecast a rosier future, with more jobs and prosperity for Europe with the euro.
"Our shared aims - high levels of growth and employment for all - depend critically on its successful introduction," he told a special session of the European Parliament.
And despite years of controversy, the strong political support for the euro was shown - the only opposition over the weekend came from extreme left or extreme right parties. Mr Jean-Marie Le Pen, leader of the French National Front, denounced the decision to "approve the death of 11 national currencies. This vote will stay with you like a stain from the blood of the 11 nations that you have sacrificed."
But for most others, it was a time for determined optimism. This will herald a new era of economic growth and employment gains, Mr Brown said. And it does seem all participating countries are determined the project will succeed.
But the depth of the disagreement over the central bank job which emerged over the weekend - and the messy compromise "solution" - have overshadowed the launch of the new currency.
The compromise, which saw the Dutchman, Mr Wim Duisenberg, win the job - but only for around half the full eight-year term - will inevitably lead to fears the job is now more politicised than many of the countries would want.
Indeed, the brinkmanship of French President Jacques Chirac - which means his man Mr Jean Claude Trichet will take over the job in 2002 - means Mr Duisenberg's authority is weakened from the outset.
What this means for the credibility of the new currency remains unclear, but market reaction today to the deal is likely to be negative.
The central bank president will be one of the most powerful men in Europe and will have complete responsibility for curbing inflation across the entire euro zone. It will be the president, along with his vice-president and four fellow council members, who will set interest rates for all countries across the euro bloc.
It is no exaggeration to say the ECB will be the most powerful Union institution ever. The president will effectively have power comparable to the US Federal Reserve chairman, Mr Alan Greenspan, who controls US monetary policy.
Mr Greenspan's every word is weighed by the money markets: a single remark can and does move global stock and currency markets. If the euro is to challenge the dollar, then the president of its central bank must also be a powerful, respected figure, seen to be politically independent.
But the deal at the weekend may have weakened Mr Duisenberg. By the time notes and coins are issued in January 2002 there will be more focus on when he will step down than on what he is saying. That could mean a weaker euro with higher interest rates than was expected.
The other problem, from Ireland's point of view, is the very small representation of smaller countries on the ECB executive board. Only the Finnish central bank governor, Ms Sirkka Hamailenen, can conceivably be seen to share our preoccupations.
Also, despite Irish concerns that there should be no permanent members, it now appears the four larger countries will always have a seat on the board. And, if and when the UK joins, it is seen as taking over the Dutch seat. This would leave only one seat for all the small countries to fight over.
This shows how much we are throwing our lot in with our EU partners. The new "euro land", as many have taken to calling it, will mean Ireland is now economically linked to countries from Finland through to the Italy and over to the Balkans. The area contains some 290 million people and will rival the US in terms of economic power.
Europe's official data bureau said on Friday the 11 countries selected to from the euro zone would become "the biggest commercial power in the world." Exports from the 11 euro countries were 25 per cent higher than US exports and double those of Japan last year.
The €11 will have a total population of 291 million, with 269 million in the US and 126 million in Japan.
Advocates insist the euro will boost business in participating member-states by stimulating cross-border competition, leading to lower prices for consumers and greater competitiveness, as well as a strong currency.
The strict budget discipline, which goes even further than that negotiated in Dublin under the Stability and Growth Pact, strengthens the system. This is expected to boost the currency, as it will help finance ministers resist domestic pressures for expansionary budgets. Mr McCreevy will now have to agree the broad outline of his budget in Europe before he can announce the details in Dublin.
However, critics argue unemployment could actually rise as countries loose the ability to control their own interest rates and adjust their economies.
The problem for countries such as Ireland and Spain, which are growing faster than the core countries of Germany of France, could mean interest rates are too low to hold inflation in check. And as inflation rises, competitiveness will fall and jobs will be lost, they argue.