Fisher said that FX markets are "manic-depressive mechanisms".

"The mood comes and goes," Fisher said, noting that the days of the vvery weak euro exchange rate against the dollar were not so long ago. Fisher said that central bankers should not react to short-term movements in exchange rates.

From Q&A as reported by Market News International

I truly believe that a nation or region benefits when its currency becomes an international reserve currency.   To sustain that status, the monetary authority must show that it will remain committed to protecting the purchasing power of its currency.  Global competition for international reserve currencies gives central banks an added incentive to pursue that goal. 

The dollar is widely used as a transactions medium, as an invoicing currency and as a currency of issuance for international bonds. The euro has made some inroads in all of these areas—not least as a transactions medium, where the existence of €500 notes has enhanced the currency’s attractiveness relative to the dollar in the cash economy—but at nowhere near the pace that some analysts had predicted prior to the currency’s launch. I would expect the euro to continue to grow in importance as an international currency in coming years.

The phrase "international role of the euro" covers a number of disparate possible functions of the currency. These functions include the use of euro-denominated assets as official reserves, the use of the euro as a vehicle currency in foreign-exchange transactions, the denomination in euros of financing instruments issued by borrowers not resident in the euro zone, the acceptance of euro-denominated or euro-linked assets in international investment portfolios, and the invoicing in euros of internationally traded goods and services. Of course, during the post-World War II period the U.S. dollar has been the dominant international currency with respect to each of these functions. It seems plausible that the euro, a low-inflation currency used by an economy comparable to that of the United States in size and sophistication, will, over time, increase its "market share" in each of these areas.

Although economists and financial market participants will observe the developing role of the euro in international transactions with interest, the direct benefits to euro-zone economies of having the euro play an international medium-of-exchange role are relatively modest. Arguably, the more significant aspects of the euro's international role arise from the strengthening and expansion of euro-denominated financial markets as these markets take on a greater international character.

Should globalization be allowed to proceed and thereby create an ever more flexible international financial system, history suggests that current imbalances will be defused with little disruption. And if other currencies, such as the euro, emerge to share the dollar's role as a global reserve currency, that process, too, is likely to be benign.

We are left with the question of how the international role of the euro will unfold. The attraction of investing in dollar-denominated assets depends upon relative rates of return. To the extent that the capital flows we have observed from Europe to the United States are a critical piece of the story, the future will be determined, at least in part, by the success in Europe of matching the expected rates of return on U.S. assets. But market pressures toward portfolio diversification are clearly also going to play a major role in the future relative positions of the dollar and the euro.