The only place most English readers encounter the umlaut is in metal band names and IKEA. Both signify foreignness to us, but the intended effect is quite different. IKEA wants to convey European cleanliness, modernity, and simplicity, while metal bands use the umlaut out of a sort of metal tradition to convey Teutonic power and barbarianism.
Linguist and language historian Arika Okrent explains the origin of the umlaut and how its different uses can clash embarrassingly. -via Metafilter