If you are travelling from a regional airport, check out low-cost carriers flights to Marrakech, it might work out a lot cheaper than the group flight. It's really easy to get a taxi from Marrakech Airport into the city if you decide to travel on your own (agree the price before you or your luggage get in the cab though!). The scheduled Royal Air Maroc flight sometimes goes via Casablanca, and might get you into Marrakech very late - I flew with them once and didn't get a flight at all from Casablanca, we had to get a bus and arrived at the hotel at 4am. I travelled on my own for this trip but the rest of the group didn't arrive until 5am, which made the first day really tiring for them.
The CAF refuge is a bit sparse and can get crowded. We asked if we could stay in the Mouflon Refuge, which has a lot more space (and toilets) and is apparently cheaper, and our guide arranged this for us. Neither is particularly warm in the winter, so definitely keep warm dry clothes that you can change into when you get back from your days out. The fire at Mouflon is definitely warmer ! Having said that, the trip doesn't get a 'Tough' rating for nothing.
Take a few books and games for days that you get snowed in.