Originally Posted by Aviatrix
Countries in Western Europe, especially the smaller ones, are quite used to the idea of accepting next door's currency. I don't actually think you'd have much of a problem spending Euros in Copenhagen - Danes are used to cross-border visitors (especially from Germany) spending their own currency. (I grew up in Northern Germany, not far from the Danish border)
Try spending Swedish kronor in Denmark .... and it's not easy or wise nowadays. The Germans -- and also other euro-spenders -- have it somewhat easier, but the Danes were taking German marks far more readily and "affordably" then they take euros nowadays.