I actually negotiated the possibility to take one day off per week at my own discretion, thus working flexibly between 80%-100% in ~5% steps. In my mind this is a compromise with my dream of early retirement "Mr Money Mustache"-style.

Early retirement is just something I don't see happening for a salaried worker in Sweden. Comparatively low salaries (for developers), high real estate prices and high taxes makes that pretty impossible. But now I have the choice of either taking a day off or pay 61% of my salary for that day to the government.