Located a bit out of the beaten path in Töölö, but well worth it for tram fans like me. The location is an old tram service hall, and there are nice vintages standing around.
The espresso was decent, but nothing extraordinary. I'd guess Segafredo. Visited in early afternoon, so it was very quiet. A bit spookily so, in fact. No background music or other noise, and a big curtain along one wall was absorbing what little noise there was. The few other guests sort of got into a whispering conversation, and you could still hear them without effort.