I've seen them around for a while, thought gimmicky myself. But a few co-workers use them and highly praise them. They are not for cutting anything hard --frozen foods, meat with bones etc., but for veggies etc they are said to be great.
I saw some links but didn't copy them. I guess the attraction is they are sharper than steel-- and a bit different also. I would suppose a rel hard cutting board would be out of place.
My main question is if they do loose an edge how to you sharpen them? Maybe not at all. The reason for not cutting hard stuff is so you don't chip the edge. Though I might get some users advice here.
Looked via google and found this link about ceramic knives vs steel knives, need to look through these myself when I have time. http://www.google.com/search?client=safari&rls=en&q=ceramic+knives+vs+steel&ie=UTF-8&oe=UTF-8
After reviewing about 8 different sites, I think I'll stick with my carbon steel knives (and not stainless steel, either - carbon steel holds a much better edge). I've never had one discolor on me and I slice a lot of acidic foods. And I've never noticed any metallic taste in foods when I slice them with these knives, either. I think the ceramic knife manufacturers are overstating that point.
EDIT: Here is a thread on this board from some time ago. There are some interesting points here:http://www.barbecuebible.com/board/viewtopic.php?f=2&t=19684
As for sharpening ceramic knifes if they get a nick, from what I read it isn't possible. They'll also apparently shatter if you drop them on a hard surface. Steel knives don't do this.
And sharper than steel? I was going through some of my tools and it turns out that I have a couple of work knives with ceramic blades. They're sharp, but not that sharp. By comparison, I can shave
with some of my steel knife blades - in fact, that's the test I use to see if they've been honed well enough.
Your mileage may vary, but I think I'll pass on these.
However, I might spend some cash on one of these rigs instead: http://www.leevalley.com/en/Wood/page.aspx?p=67152&cat=1,43072,67090