Looking good Kurt, personally ive only just scratched the surface with it, just gettingthe basic tools down, and getting used to the projection master, droping and picking up, using alphas for bumps etc) I'm waiting for a tablet before gettin really into it as its a right pain with a mouse!
Mirek - Have a look on Kurv studios, thats where the link for the free tutorials are.
Z brush is great, once you get the basics of how to model its very intuitive to get really good results, fast.
You still need to have a good base mesh to get the details in where you want them, without going to really high poly counts (such as loops where wrinkles will be for the mouth etc..). although its not a pre requisite as you could jut grab a sphere in Z brush and go from there sculpting (good way to get into it without getting bogged down in the detials)
"No pressure, no diamonds" Thomas Carlyle