I stayed here for a couple of nights and was thoroughly impressed with the accomodation.
The staff were very kind and helpful. The room was kind of small but I loved the idea of sleeping in the converted attic space so that was fun. Robes were provided so you could use the pool (and sauna which I didn't use) for a small additional fee each day if you wanted. The pool area is quite beautiful.
Location is fantastic. We made the short walk from Alexanderplatz on our first day but then used rental scooters of the U-bahn around the corner to whizz off to the daily itinerary. Plenty of places to get coffee and lunch nearby too.
Would highly recommend this accomodation if you like the room concept, but be careful as the ladder to the beds is very steep.