Very nice rooms - basic, but clean, tidy, well appointment and comfortable beds.
The Spa / Sauna area and pool are very, very nice.
The meals in the restaurant were excellent, and the Bar / Bistro is great.
The problem is noise outside the hotel.
Because there is no A/C in the building, if you want to cool down the room, you need to sleep with the window cracked, which is fine. The problem is that there apparently a frequently traveled ambulance corridor right along the hotel. Sirens and all, 24 hours a day. Also, at 6am on the dot, flights start at Tegel, whose flight path goes directly over the hotel. Even with the windows closed - they don't seal well enough to keep the noise out.
I believe the flights end around 10pm, but if you have a late night at all, plan to hear jets taking off for a 6am wakeup call. Every day.