I fiddled with z-brush for a while but it's hard for me to wrap my brain around more then one programming interface. I probably only use 2% of the features in Maya.

I tried to use maya and 3dmax for a while and ended up unlearning both packages, because my brain started mixing up the keyboard commands to the point I could not use either package efficiently so I just switched back to Maya and Maya only.

That being said the Photoshop or Sketchbook -> Maya -> Z-Brush -> Maya -> 3DPaint/Photoshop pipeline is sticll incredibly powerful.

I wish I had the brain memory space and time to learn to use them all. As it is I have been using most of them for a while and have barely made a dent in understanding their full capabilities.