My husband & I had a lovely time staying at Axel & Anne's apartment - great location close to lots of parks, cafes and just a short walk from train stations which will get you to anywhere in the city.
Axel & Anne were incredibly accommodating and flexible - they even lent us their DVD player and offered to pick us up from the train station as it was pouring with rain when we arrived!
I would recommend this place to anyone wanting to visit Berlin and stay in a lovely clean, light and comfortable apartment.
We'll be back I'm sure!
:)