My girlfriend and I came back last week from a stay at Roi's and (as expected) the flat was incredible. We could not have asked for a cleaner, more luxurious apartment. Roi was kind enough to allow us to arrive a little early and drop our bags; we were met by his lovely cleaner who gave us all of the information we needed about the local area and public transport. She even walked us half way to an area of restaurants she recommended.
The area where the flat is located is perfect (3 minute walk to the Ubahn) and with plenty of shops.
The flat made our stay in Berlin 10 times better and we would highly recommend staying with Roi to anyone who asked.