I've eaten here three times in the last two years and highly recommend it. The setting is an urban villa that is just a stone's throw away from the Lazienki Park (which is probably the most beautiful in Europe, the world?). The immediate surroundings are non-descript but there is good bus and tram transportation. The rooms are quite elegant, furnished with Polish country antiques. Embroidered tablecloths. Excellent classic Polish cuisine: soups, roasts, fresh-water fish such as carp amd pike-perch. Some game too. Lots of forest products used: mushrooms, wild berries, herbs.
Last Saturday I had cold Lithuanian "chlodnik" (beet soup with sourmilk and thin strips of roast veal), beef paupiettes ("zrazy") with buckwheat groats and mushroom sauce, plus homemade blueberry ice cream.
Service is polite and efficient but don't expect too much real expertise. The brains are in the kitchen. Wine list is ok but over-priced. The only beer is Zywiec - no longer the best in Poland.
Complete lunch for two with a bottle of Zin was 80 euros. Everyone speaks Restaurant English.
I can't praise this place enough. I live in Paris (the City of Lousy Food) and would love it if the Tradycja were here.
Their web site is http://www.restauracjapolska.com.pl/