Sculptris is one of the most used sculpting software, is really easy to use, the brushes are really great and the dynamic tessellation is amazing, is a great tool to start sculpting or if your budget is low.
You can export obj, and textures to an external 3D and 2D software
The UI is pretty easy to learn, and you have symmetry and you can use the alphas from zbrush central download section.
This software is key to have a complete suite of 3D if you already have Maya, 3dsmax, Blender, etc. this is an amazing free tool for the sculpting process.
In the website you can find a few introduction videos as well.
the function of GoZ is limited, you need to install zbrush to enable.
A render function would be great (not limited to screen size)
Great sculpting tool, you can texture and export to other 3D software to make the retopology,
And the best of Sculptris is FREE