Quote Originally Posted by EPT1955
The reviewer mentions a pincushion effect and I have a hard time getting my arms around this concept. I am not sure how this issue would impact my photography efforts.

You probably won't even notice it, because it's not that bad. And with the newer software it's very easy to control by lens-profiles. In the test the squares should be totally square, but with pincushion distortion they are slightly pushed inwards. While with barrel-distortion(mostly seen by wide-angle lenses, it stretches the boxes. Seen here for instance(in a worst case scenario)