We loved the simple, modern architecture and styling of KCB (some reviews say souless and bare, we thought minimalist and clean). Particular highlights were our private roof terrace to look over the desert region for sunset and sunrise, our bathroom with deep sunken marble bath, double sinks.... sigh! The pool is every bit as stunning as the photographs show and the hammam is an enormous underground dark red marble cavern.
We found the service attentive and discreet. It is not a "click your fingers" type place because, frankly, it is large and the staff don't hover in view the whole time which, for me, I like. I wanted to feel like I was there on my own in a private palace! Having said that, whenever I did try to lift a finger (moving my sunlounger into the sun) staff came running from, apparently, nowhere.
This was our first two nights in Morocco before heading to a riad in the medina for two nights then three nights on the coast. We wouldn't recommend staying there if you want to "do" the Medina - as other reviewers have said, better to go and stay in a Riad for that, but it does offer the space that you cannot find in even the most ritzy and boutique riad in the Medina.
The food was very good but the menu stayed the same for both nights we were there - if we had stayed for another night we would have ventured into the city for some variety - for that reason, two nights was enough. The breakfasts and lunch were varied and fresh/exciting.
Finally, it is expensive but for such a stunning building you can see why. Note of caution, extras mount up VERY quickly with eating lunch dinner and any treats in the spa....