Personally I think they are not worth the money.
They say that they stay sharp for longer, and while that may be true on a technical level, practically they chip really easily, diminishing their effective sharpness really quickly.
I got through roughly 3 months of normal use, before it had deteriorated substantially, and since you can not resharpen a ceramic knife, I had to throw it away.
I think you are better off with just buying a whetstone and periodically resharpen a metal knife.