Thinking of getting a shaman for my Gitz. Question is which kind.
The Fungoid seems to be the no brainer: more durable, better fighter, and possibility to crank extra command points every turn.
However, the Madcap's unique spell--Nightshroud--is really good, especially against Overlords and all that shooting. They *also* get access to actual artifacts, among which the Moonface Poppet seems particularly handy.