I used the app four times since I moved to Sweden 2 years ago. I haven't touched cash, actually I am not sure how the current notes/coins (they changed them) look like. If you shop in stores/restaurants then you use cards mostly. Swish in my experience is for splitting bills (less common), at after work parties when someone buys beers and you pay them back, for very small vendors who do not want to bother with banks for getting CC terminals.