20 waisted years in my humble opinion.
When EU countries could have been forging ahead, building on the natural base of social democracy and technological advancement, e.g. to become world leaders in future energy . Instead they have spend 20 years dealing with the internal inconsistencies and self imposed limitations of a single currency without a single fiscal / monetary policy.
I don't see it changing, but who knows.
EDIT. I do wish people would post counterpoint, rather than vote down something that I explicitly stated was my own humble opinion, and indeed ended on a conciliatory sentence.
Down votes really should be used for trolling, or off topic to the poster they are replying to, not as a lazy way of replying.