What differences could one expect in the different regions?
The basic information from Wikipedia:
Dialectal variation of vowels
Dialectal variation of consonants
Talking to people from Krakow, they mention that the enunciate more or emphasize proper letters more.
In Warsaw, or central Poland, consonants at the end of words like brat
remain voiceless, in the first case, and in the second, they are devoiced, so they are pronounced like brat
, while in Cracow and Poznań, that is in the regions of Małopolska and Wielkopolska, they are pronounced as voiced: brad