Spent 3 nights recently at the Artotel Berlin Mitte.
It was supposed to be a designer hotel, I have searched for the design, but I haven't found any kind of design in the rooms. May be the restaurant have something, but the rooms are poorly decorated, with common furniture. The bed was not very comfortable. In the bathroom there is only liquid soap with two small towels.
Do not expect any kind of luxury at Artotel Berlin Mitte, it is only a basic hotel, but with a convenient location (50 meters from the metro, 2 metro stations from Alexander platz).
The breakfast was good and the staff friendly.