I have been impressed by the accuracy of 23andMe's ancestry reports. My grandparents are from four different European countries. Two locations matched my maternal grandfather, (Württemberg, Germany) and paternal grandmother (North Brabant - Belgium). A third predicts my paternal grandfather (Estonian) had roots in Finland. The fourth is somewhat surprising. with a "possible match" in Poland and a "likely match" in Vilnius, Lithuania. We know little of the ancestry of my maternal grandmother other than she came from Poland. Her married name was "Roman" and the maiden name of her mother (as shown on her marriage to my grandfather) is "Bartlet" (which seems to me an unusual surname for Eastern Europe.
I would be interested in any thoughts or comments that might give me further clues regarding her ancestry.