Especially when it's a sizeable one and you haven't read any books for months and months ( Just tore through Christopher Isherwoods 'Goodbye to Berlin' )
Put it on during breakfast and it absolutely stoked my joie de vivre. Beautiful, whimsical UI too. Pick a country and a decade, and let it transport you.
Incredibly low-maintenance. The technology is unassuming yet so chic. Cheapest way to develop your coffee palate, plus the distinction of saying “I make my own coffee.”