These post-communist days, good. After 1989, Poland entered the capitalist world with a vengeance and has spent the last 9 years making up for lost time. You can spend a lot in the boutiques, or a little on the sidewalk vendor or in the open-air market. If you're looking for items particularly Polish, be on the watch for wooden carvings, amber, lacework, linen embroidery, and posters.
Polish posters are renowned , and can be gotten quite reasonably in the off-tourist sites.
Although the stores have changed, some of the communist habits remain. Baskets, which regulate the number of people in a store, can usually be found somewhere near the entrance. If you don't see any, wait until a departing customer empties one. Note, you will be chastised if you are without one. Even if you're a tourist and a foreigner and don't understand Polish, they won't let you get away with it.