Had a great stay at Dietrichs, the flat has everything you could want, especially the very powerful shower which was great! The only thing we missed was a double duvet rather than 2 singles but it didn't spoil our stay at all.
Use of bicycles was brilliant - we cycled everywhere which saved us paying for public transport. The roads are very bike friendly all over Berlin and I never felt in danger. Only thing was the lights on the white bike didn't work but the roads are well lit even at night.
On the first day there were roadworks outside quite early but Dietrich was very apologetic and accommodating, even gave us a partial refund as a goodwill gesture which was very kind.
It is about 30 minute walk from Alexanderplatz and a 10 minute cycle, so very central, and there is a corner shop on the street and a 24-hour shop just down the road.
Would definitely recommend this place and we will be staying here again when we come back to Berlin!