I just received this as a Christmas gift; have been excited to try it.  Although I’d heard that butternut squash was probably not going to work, I wanted to try and find out why.  The plastic anchor that is closest to the machine (not the skewer end) simply carves out a circular chunk from the squash so it can’t rotate.  If this piece were more robust — perhaps made of metal or at least comprised of sharp spiky teeth that were a bit longer — it could easily work with harder fruits and vegetables.  Seems like an expensive attachment for such a limited list of produce.