Stayed with Alan and Kasia for 26 days and for those that want the quick review:
Simply awesome place and hosts, excellent in all aspects, absolutely recommend for any trip to berlin. Highly professional yet approachable and friendly.

Long review
Apartment: In Pberg which is the hip younger part of berlin, the place is centrally located next to a big commerical hub but is on a lovely quiet street where the noise level is very low. The apartment itself is beautiful, modern, clean and well equipped for both long and short stays. There is a 24hr supermarket 2 min walk away as well as a large metro station. Lots of local shops near by for haircuts and other services that are reasonably priced and with out most of the pomp of alexanderplatz or the mitte.

Hosts:
Alan- love this guy, easily could spend 10 hours talking about all sorts of stuff and did. He is ultra friendly and is highly knowlegeable about all the good stuff to do in berlin both for tourists or those that want a more engaging experiance.
Kasia- a lovely and extremely well organized lady. She is friendly yet logical and engaging. If I needed a manager for anything I'd hire her in a heartbeat.
A&K:Can't say enough good things about her and alan (only have a 1000 words in a review) Though they had me seriously consider moving to berlin lol!
Berlin: its quiet a city, always fun and unrestrained.
Value: I found it a great value for europe both the city and especially the apartment. Had several friends ask me for their card after they saw the apartment because they found it so superior to their accomodations (both hotels and other airbnb places).
overall: simply awesome, thoughly enjoyed the experiance. Highest recommendations to anyone looking to stay in berlin buy wants to have a more real experiance where you can feel at home and go at the pace and style you'd prefer. After this I would never consider staying at a hotel or another airbnb in berlin. Planning on a return trip very soon and most certainly will only consider A&K for my accomodations.