Overall the stay was great and Fai was responsive and helpful, but there were several points that could have been better:
-The apartment is on the 5th floor (4th floor to Europeans), with no elevator.
-The two couches (including the dark green sofa mentioned in the listing) are more like love seats. They are not really long enough for an average-sized person to comfortably sleep on.
-The blankets on the bed were rather small (compared to the size of the mattress). I am 6'0" (182cm), and was unable to have my feet and shoulders covered by the blanket.
-The towels had a slight mildew odor. I spoke to Fai about this and she quickly had Oksana bring replacements, but those had an odor as well.
-Fai's guidebook had a LOT of rules, including sternly worded admonishments about having the police immediately remove us if the neighbors complained. It was not a problem to follow the rules, but the wording made us feel a little unwelcome.
-The nearest train line (the U4), is one of the less convenient U-Bahn lines in Berlin. You will need to make an extra transfer for most journeys.
Aside from these issues, are stay was great.