Masters of doom portrays carmack as a total dictator of a boss. Doom Guy by John Romero seems to back this up
In Doom Guy, though, Romero says that after he left iD, he heard from others still working there that the company had become something of a dictatorship under Carmack, and that within X months (I forget how many), half the company had quit. Romero also qualifies several times that they were all in their early/mid-20s and didn't have the requisite life experience to be handling business situations well