It's true that you can work with really dense models (millions of polys) then convert all of that detail to a displacement map that you can apply to a much lighter model. It also has some great sculpting tools that let allow you to work really fast. You could easily start with a sphere and in an hour or two turn it into a werewolf, etc..... You can also use Zbrush to make bump maps.. Oh, and you can paint with Zbrush. I love the paint brushes and other special tools that it comes with.
The thing that I don't use Zbrush for is laying out my edge loops. Zbrush really isn't designed to work with individual edges or faces. I always lay out my mesh is Maya then bring it into Zbrush to model. I usually bring the model back and forth between Maya and Zbrush so I can get the best of both programs.
Zbrush isn't hard to learn but you'll have a hard time if you just sit there and read the manual. You have to actually work on a model to understand what they're talking about. I think the average CGI person can figure out the basics of Zbrush and begin making models in a few hours. AFter that, you start learning about all the other things it can do like lay out UVs, create custom brushes for bump maps and displacment, etc...
I should mention that Zbrush also has its own render engine so that you can produce really nice renderings too.
I love Zbrush. It makes modeling easy and fun.
Check out my site if you want to see some behind the scenes pictures of some of my models that were created with Zbrush.
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