Not in some places you like Harry ...like namasteindia restaurant on nowegrodska
I was in Namaste on Nowogrodzka a couple of weeks ago and had no problem with paying by credit card. But I guess it must be hard for you to know things like that, given that you're sitting in your cornershop in New Jersey.
buying tickets from drivers i the local buses
Given that I have a monthly pass, why would I want to buy tickets from bus drivers?
There are many 'kiosks' and sometimes also ticket machines to buy the ticket, but probably also no credit card will be accepted.
I can't remember the last time I wasn't able to pay at a kiosk with a card. Oh, and the ticket machines in Warsaw also accept cards (or at least the ones at the tram stops do, the ones in the trams are coins only).