Cerakey offered me a sample of these ceramic caps, and I received them today:
I’d like to stress that I received these for free but my opinion is honest, I don’t have any agreement with the company.
So these are the pink ceramic caps, sitting on my pale green Keebio Jawn Founder’s Edition (which I won last year I guess). Beneath the caps are Momoka Flamingos (received from Momoka as a free sample too 
). In a world without VAT and custom fees this project would have cost me almost nothing… (I paid the shipping fee for the switches though.)
Back to the caps:
First impression: very carefully packed in nice sealed containers.
The caps are glossy but only in certain angles, so it isn’t distracting.
The surface feels like porcelain. Pleasantly smooth and slightly cold feeling on the touch. And the familiar rough ceramic feeling on the back (without the glossy layer). This doesn’t feel good at all but you don’t touch the back side of caps very often anyway.
The stem is “unibody”, so not the glued-on 3D-printed one you might see elsewhere.
The fit is VERY tight. I tried them on various switches and I kept pulling out the switches from the plate when trying to take off the cap. Regardless of the stem type (box, “dust-proof”, classic +), the tightness made me concerned.
However, it doesn’t seem to cause any issues. I changed the caps a few times, abused them even with some dreaded Box Jades (the old cap-breaking ones). But these ceramic keycap stems are much stronger than that of e.g. my very first SA set which was totally ruined by the same Jades…
This was just a small sample to populate my macropad, not a full keyset, so I couldn’t test real typing. However, I keep touching and stroking these caps, and resting my fingertips on them. Which is telling.
If you are interested, Cerakey offered a $5 discount for those using the “KBDNEWS” coupon code (this is NOT an affiliate thing, I don’t get any commissions). And they’re currently running a kickstarter campaign to fund the full ceramic set if that’s your thing.