Split feelings.

Sure it makes it easier to travel around Europe. Last year I did a small trip - starting at the German MudGathering in Münster going thru the Netherlands and Belgium to France. I needed 4 kinds of money, loosing heavily at each currency exchange...

On the other hand, the German Mark was the most stable currency within the 12 Euro countries... But since the exchange rates got fixed 3 years ago, I could not find a bigger inflation than before. Sure some shops tried to make a win by not calculating the prices in the Euro by the exact rate - but in general prices have not risen more than usual (nothing gets cheaper...).

For me, the positive aspects are more important - prices are easier to compare across borders, no losses when traveling... (very nice when you live near a border like I do - you do not have to think about money exchange when you go for a day skiing in Austria).