Yeah, ceramic knives get a bad rap but they have their uses.
I have a lot of knives (and have made my own) and I love ceramic knives. For those that don't know, ceramic knives are sintered zirconium dioxide; they are super sharp and retain sharpness far better than steel, but are brittle and not practical to resharpen. As a result your average knife enthusiast tries them, sees that they chip easily and can't be fixed, and condemn them as throwaway garbage.
The secret is to use them for an application where they'll never hit something hard or rough. For example, using them where they might hit metal or bone, they'll eventually chip - possibly into your food! Or using them on a cutting board, they'll dull, although slower than steel. But use them on soft objects only and they'll last virtually forever.
They are very useful for cutting cardboard boxes open, or tape, or plastic. You can use the same ceramic knife for 1000+ cardboard boxes and it will cut like a hot knife in butter, while the same steel knife would need to be resharpened several times for the same smoothness.
Oh, and they are non-browning for food like apples or avocados, which is nice. The browning you see in cut foods is caused partly by polyphenol oxidase, an enzyme that can be activated by iron and other metals. Steel knives shed tiny amounts of iron into food as they cut, so if you use a ceramic knife, your food will look fresher for longer.
