Me and my friend stayed for 4 nights a couple of weeks ago and had the most wonderful time. The experience was great from start to finish. Betty got in touch very quickly to confirm everything, and kept in touch in English which was really useful for me (I tried to learn some German beforehand but was rubbish - sorry Betty!)
The apartment is very cute, stripped back floors, high ceilings and lots of lamps and nice little touches. Because of the size of the place and it being January/February I was worried it would be cold but it was warm for the whole stay.
As other reviewers have mentioned, there is a lot of noise from the cafe next door. The cafe opening hours were 12-7 and within those times the sound from the music, coffee machine and furniture could be heard pretty loudly in the bedroom and the communal area. This will not be a problem if you plan on being out all day, as we mostly were - it only bothered us when we were nursing a hangover one day, but that was completely self-inflicted and we didn’t feel the need to bring it up so not a problem at all...
The location was fantastic, 60 seconds from Schönefeld station and walking distance to lots of cute bars and cafes, 24 hour shops, a few takeaways. Having the cafe next door was great - we got tea and a delicious vegan carrot cake to help with that hangover...
Definitely recommend staying with Betty, 10/10!