Adm1,
Myself and the missus stayed in the Derag Hotel Grosser Kurfuerst(4*),a weekend Germany were playing in Berlin during the world cup and I have to say that it was really nice.Very impressed.Even during the world cup it was cheap considering.Found it on hotels.com but then went direct to the website and got it even cheaper and that included breakie!Well recommended!Location was spot on,right beside a U-Bahn stop,very central.
Enjoy!