Riad Cinnamon is a delight. The suites are impeccably decorated in local style, our bed was very comfy indeed, and there's aircon in all suite. Not that that matters - the building is cool and fresh throughout even in the midday heat; while the plush rooftop terrace offers leafy shade or blazing sun as you wish.
Service is utterly beyond reproach. Our hosts (Hassien in particular) could not have tried harder to please, and nothing is ever too much trouble.
Breakfast is generous, fresh, and served on demand. We also had dinner in the riad on our first night; it was also excellent. If you've flown in during the afternoon, do eat on-site for your first night; as food is not a highlight of Marrakech - you might as well make yourself at home. (There are excellent tagines etc. on offer in town, but you won't be missing out).
Marrakech is a full-on city, and Cinnamon is in a relatively impoverished part of town (yes, all these things are comparative). Although you are unlikely to come to any harm, you are going to face a barrage of salesmanship and occasionally either anti-Western sentiment or good old-fashioned con-artistry. I suspect the city could be challenging for e.g. single women. At Riad Cinnamon, we were offered a phone in case of any problems, and the staff were adamant that they would come and rescue us from anywhere if we needed it. Very reassuring, and utterly charming.
I heartily recommend Riad Cinnamon to you. It's central, charming, and staffed by heroes.