I'm away for a week and Pixolgic announce they are now developing Sculptris. It would be interesting to see if the features will be incorporated in a future release of ZBrush:
http://www.zbrushcentral.com/showthread.php?t=090617
From a quick 5 minute play with this new Alpha 5 version, it does appear more stable than before. Subdivisions for the Standard brush appeared to be locked after a few edits, though the Grab brush created more subdivisions as the surface is pulled out. Looking pretty good so far...
