First, I must state that I own four other pair of Keen shoes. I love Keen shoes but not these slippers.
If you thought your sweater pilling fierce, it has nothing over these slippers. I have owned these for less than two months and the pilling is so severe that I walk around in slippers that look as if they have mange.
Nevertheless, they're structurally fine, and will now serve as an extra pair of slippers, because I've already replaced them.