Just received the new Zbrush 4r2b and found an issue with MorphUV. For some reason it seems to really chug the system when unfolding the model to its flattened layout (even at 2 million polys). Compared to earlier versions this process is way slower but I noticed this version is a lot more RAM hungry (so maybe that’s why).
Worse than this, after painting on to my model all the changes are lost on hitting MorphUV to go back to the original state. Normal polypainting on the 3d/unflattened model is fine so it appears to be limited to Morphed/Flattened layout.