My experience is that most places where I buy stuff for above SEK 500 accept AmEx. Smaller shops usually only accept Mastercard/Visa. The one real exception to that rule for me, is my auto mechanic, who doesn't take AmEx. Willys and Lidl started accepting AmEx a few months ago. The only grocery stores that don't accept AmEx right now are the smaller immigrant stores. So, for me, 80-90% of my purchases are with AmEx.