I had a lovely two nights stay here last month. The staff were all friendly and attentive, and the room was spotless.
The bed is very comfortable (with a plug socket on either side), and the shower powerful. A comfy armchair and an opening window add to the room. My room (515) faced the inner courtyard, and even with the window open was quiet.
The breakfast was great, with a range of teas, condiments (including local honey) and a hot selection.
The tram outside was a bonus, I used it a few times each day, and the S-Bahn is next door. Downstairs is a DM, an apotheke and a REWE, so any supplies you might need are right nearby.
Would happily stay again, if in this part of Berlin.