Spent a couple of days in Ray's apartment and loved it very much.
The location is great, very central yet not crowded and the atmosphere in the neighborhood is great.
The apartment was quiet despite the bar downstairs.
The apartment itself is well furnished and has an interesting style, plus it clear that there was an extra thought given towards making our stay more memorable (chocolate on the pillows and wine).
In addition was very clean and easy to find and get into.
All in all I really recommend this apartment for a single or double looking to spend time in Berlin.