What a great find! This is our 4th visit to Berlin in the last couple of years, but definitely the best place we've stayed. The location is absolutely perfect, the apartment is very close to Alexanderplatz, the Hackischer Markt (with the beer kellers and restaurants), 2 major underground lines and the tram network.
The apartments are very new and clean, and have been created to a high specification. Very well laid out, comfortable furniture and very clean. The morning croissant and fresh coffee was a welcome added bonus too. Staff were friendly and helpful, but not overbearing. Our apartment was on the top floor and we enjoyed a view of the Fernseherturm (TV tower) from our little balcony.
I would highly recommend these apartments, we'll definitely be back!