From Wikipedia:
Max was the first hamburger restaurant ever to outcompete McDonald's restaurants, which happened in 1991 in Umeå and Luleå, where McDonald's (who were later to arrive in northern Sweden than in Sweden's major cities) in fact closed their restaurants before returning a few years later. In 2007, the popularity of Max forced the McDonald's in Skellefteå, Piteå and, again, in Luleå out of business.
For four years consecutively, Max have had the most satisfied customers among the nationwide fast food chains in Sweden, beating McDonalds and Burger King by far, in polls conducted by commercial agency ISI Wissing AB. This may be due to the fact that Max hamburgers are never cooked before they are ordered, even if it means that an order generally takes somewhat longer to be completed than what is typical for fast food restaurants.