What I really liked: location, privacy, price, convenience. This stay is right next to Neukölln's S-bahn station, and it's especially convenient because that platform can take you straight to Berlin's airport. Since it's studio-style and check-in is remote, I didn't have to fuss with management unless I needed something (they have a hotline--our shower did not drain and flooded the bathroom, and they came to take care of it first thing in the morning). The price was excellent for the length of my stay, and everything was easy to manage. Maintenance and housekeeping were friendly and polite.
What I wish I knew before staying: the size of the apartment. This stay is cramped for two people who are not sharing the bed. I would say The Rix is ideal for a single person's booking. With two people, we had to reorganize the room to first fit our things, and then every time we wanted to open the balcony door, or cook.