It is a very stylish, comfortable and quiet apartment in the heart of Kreuzberg. . We even got our netflix working on the big flatscreen. We liked the restaurant suggestions (schnitzel at Joletsch and pizza at Casolare). Next to the apartment is a really nice coffee place. The LPG bio market has fresh and even organic bread. We didn't meet Philipp in person, but the communacation was quick and helpful.
The only downside (we knew in advance) is that it is on the fourth floor with no elevator. This means a lot of stairs and precisely 90 steps....
Besides the S-bahn closeby it is also very easy to rent a bike and cycle through all the highlights of Berlin.