We are under Carmen with my present employer. Carmen has ruled us for about two years, and the benefits of bying a such rather complex system has not yet been discovered. The system has a lot of parameters for the scheduler to play with, to ensure maximum production of crews at all times. The problem seems to be that Carmen is happy as long as you are on duty, i.e you don't have to be flying on the balcony yourself, you can just as well fly as deadhead for a half day, produce one flight, and be deadheaded back to base.
The other hickup, in our system, is that our schedulers never got the proper training to learn all parameters and what Carmen actually is capable of producing...
Ciao