It's beautifully made and does the job. Some have complained that the illustrations are misleading in that it rarely takes off the entire top of the egg - but if you think on how it works then that's unsurprising: A KERDINGKERDINGER [technical term] is transmitted from the impact zone of the apex of the semi-ovoid when it's smacked by the springpulled ball down to the circular ridge which is in contact with the eggshell; now that KERPLINKING [technical term] of the shell won't rupture the sortof colloidal state of the eggwhite. No worries, insert a serrated knife and it's all off.
It makes the making of a boiled egg (especially done in an egg-boiler) a joy.
What I do wonder is: How was this invented? Hard to imagine it coming from tinkering, must have come from the thinking-through from first principles, bet was in China. No bets for who will colonise Mars :-)