Rc 75 hardness should allow for a really wicked sharp blade. I wonder how facial hair compares to the medium these things are designed to cut (thing films and foil). If it is much tougher, microchipping of the cutting edge could be a real buzzkill.
It seems that in many ways the disposable razor and the ceramic blade would be a match made in heaven. The two big complaints i've heard regarding ceramic cutlery are brittleness (breakage, microchipping) and the high cost of sharpening. As we're not sharpening our DE blades anyway (I don't think...) that shouldn't be so much of an issue. We are all looking for a sharp, smooth, and consistent disposable blade. I'm guessing that is what you'd find if you were to spring for the zirconia ceramic.
That being said, I can't see myself shelling out $14 a pop to load up my injector with these things ($20.25 for 3-hole DE).
[INDENT]Razor: Merkur 38C/GEM Micromatic/Red Tip SS
Blade: Astra Superior Platinum/Walgreens Gem
Brush: Vulfix 1000
Prep: Aquaphor, steaming towels
Soap: Col. Conk Bay Rum
Post: Thayer's Alcohol Free Witchhazel Toner, Aqua Velva[/INDENT]