We had a great stay at Nelle/Julian's apartment. You really can't beat the location. It's a lovely and quiet neighborhood and close to everything by walking or public transport.
Other than the location, another pro of this place is that it is recently remodeled. It's got great design and is a unique space, exactly what you look for in an Airbnb. Everything is new and works.
Just a couple things that we thought could be improved. First, it is a ground level apartment, so really you can't open the blinds or windows because people on the street will see you. At one point when we were trying to ventilate, and old man came and peered in at the bedroom. There's plenty of light, so this wouldn't be such a big deal, except that we were there in summer and there is no air conditioning (just a fan), so it can get a bit stuffy. However, the windows are well insulated, so we didn't feel like we suffered from outside noise. Second, the kitchen was a bit scarce on amenities. We could get by cooking meals there, but it definitely could use some more basics, for example a colander to strain pasta, bowls, and more silverware. If cooking a lot is really important for you, then I guess this could be an issue.
Overall, I definitely recommend this apartment. We really enjoyed it and will definitely stay here again when we return to Berlin.