Everyone who reads these boards regularly will know 411A's attitude towards both the concepts and the practices of CRM, so will be able to judge the value of his reply accordingly.
The more people who can contribute to the safe conclusion of a flight, who can understand more or less what is going on and contribute to it, the more resources on which a captain can call, should the need arise, the better.
As part of the team aloft, when it all goes for a ball of chalk and the flightdeck is lighting up like a Christmas tree, Cabin Crew and their input are invaluable. CRM courses should
always include them. I'll go further. For any but an all-freight airline, CRM courses should not be run that do not include Cabin Crew.