I have spent some time on various visits to Berlin at Hotel Transit. It's well located and fairly close to a subway station and easy to access.
Check in is easy and simple, the rooms are functional, clean and have large windows. on the downside they come with carpet floors and the walls are pretty thin, so if some drunk crowd comes back late at night, you hear them from far up the floor until they finally make it to their rooms.
Breakfast is nothing special, but definitely okay go get your day startet.