Question: Are there any extruders and printers that do a good job with ceramic clay?

I assume the clay has to be fine grained and with enough water added to be able to be pushed out through the extruder's nozzle. I also assume the print speed would have to be arther low for the already printed layers to gain stability before printing the next layer. Perhaps some extra equipment on the printer to spped up this drying process?

At the same time, the print speed can't be too low: if the bottom starts to dry enough to start shrinking, the object will crack.

Also, some solutions I've seen tend to result in rather low resolution/thick layers, which is negative.

So, what equipment is "out there"?

Answer: 
Here is an open source clay extruder from standard parts, that i designed
<https://www.stoneflower3d.com/projects/clay-extruder-prototype/>
Different designs of 3D printers, pumps, extruders etc. for clay are posted and discussed in the Google Community "Make Your Own Ceramic 3D Printer", driven by Jonathan Keep (<https://plus.google.com/u/0/communities/109375785524125994679>).
I cant speak for the quality or type of clay, but there are several designs out there that print in clay. Here is the first one that popped up on my google search.

<http://www.wasproject.it/w/en/wasp-launches-the-new-professional-clay-extruder/>