Apparently it's way, way worse than dropping the f-bomb.
I live in an area with lots of Poles, and I hear it a lot. I had to tell a shopkeeper off last week for saying it to an employee in earshot of the customers. Nasty. I've also told a cafe owner off for calling his (Polish) barista a malaka - swearing at your employees is not cool, in whatever language.
Hm, I had a really nice "nie ma" experience yesterday when I asked for pierogi ruski (omg pierogi!) at a milk bar and was told by the, in the words of my British co-lunch-eater, "manageress" that all they had were pierogi serem! It was like a giant bomb of sugar landed on my face. I am still full 13 hours later.