My group booked a 4-day, 3-night tour with Imagine le Voyage Tours, a company based out of Marrakech. They offer tours of the desert, Dades Valley, and Todra Gorge for groups and individuals. For $125 per person (for a group of five), we were able to rent a Land Rover with a guide and have him pick us up in Fez and do the tour in a reverse order, ending back in Marrakech.
Although Imagine le Voyage promised 2 nights in the desert in Berber tents, you must be aware that it's not with Berber families. The guide drops you off at the place where the camels are waiting, and a Berber guide leads you on the camels into the desert, where you share an encampment with other tour groups. The tents were set up in a square pattern.
Nights in the desert (especially in November) are very cold. You are provided with one blanket - the one that they hand you as you're getting onto the camel to ease the very bumpy ride to the campsite. The guides should have a box with extra blankets at the site but you should bring plenty of warm clothes.
The guides were very nice, though, and if anyone in the group decides that 1 night in the desert is more than enough, they will provide you with excellent lodgings at a hotel.
The desert near Merzouga is beautiful. This is the desert that you think about when you think of the Sahara, with rippling dunes and smooth sand. This is the one that you want to experience.
We were able to interact with some of the Berbers in Tenehir where we stopped on the second day. We were given another guide who showed us the Kasbah of Tenihir and introduced us to a nomadic Berber family. We were able to talk with one of the women and her brother and were given a demonstration of carpet-making over mint tea. Afterwards, they did ask us if we wanted to buy any of the beautiful carpets that the women of the family had made, but they were still quite friendly when we declined.