Jacqueline,
I have Z Brush and have been learning it over the last few months. I think it is a great buy at this price. There are many plug ins for it that are free and have increased the functionality of the program.
There are a bundle of tutorials available for free- find the canned mushroom

tuts that are listed on ZBrushCentral and located on Veoh I believe. He has about 15 or so videos containing may be 20 or more hours of training from basics on up.
There are tuts for sale from several venders. I can find the name of ones I bought before finding the canned mushroom soup ones. There is a blog or two that have ongoing discussion and projects. Really helpful.
I might be further along if I had not decided to expand pass the limitations I ran into with

Daz's

Carrara Pro to Light Wave 931

and Vue 6.5

. I am doing alot of learning now ad have not regretted the decision to increase my skill set and programs.