You can try Casa Camper in Mitte...I've stayed there at least a dozen times over the past 6.5 years.

It's not luxury in a coddling/over the top sense (of a Waldorf or a Ritz) but it's comfortable, clean, great staff and has an upstairs lounge for breakfast and 24h snacks as well as coffee/tea/juice, an honor bar in the evenings as well as the freedom to work if you'd like.

You're also right on top of the U at Weinmeisterstrasse and a 3-5 min walk to Hacksher Markt or Rosenthaler Platz.