Absolutely excellent hotel, which is definitely on 5 stars level, helpful staff, ideally clean and nice designed rooms. Generally, the hotel was much better than expected to be.
If I'll be again in Berlin, I'd stay there again and highly recommend this hotel for others.
The only weak point is the "arty-farty" restaurant with very short menu and ... what people say » the food is not specially tasty and definitely overpriced. But this is not big problem, because there are a lot of excellent restaurants for any taste -
Excellent location, <5 min walk to Gendarmenmarkt and 5min walk to German Dome. Closest metro stop is Hausvoigtel which is on a great line and can take you (without changing lines) to the Zoo or Ku-damm (shopping area). Wifi is free, stable, and reasonably fast. Hotel rooms are very well appointed and smart. Some great dining options closeby like Chipps for breakfast. All in all would stay again - really a nice hotel.