We got a free upgrade on arrival, which was fantastic. The staff were very friendly and accomodating, the hotel itself is smart, upmarket and clean, with minimalistic decor. We had the 30Euro per night bonus voucher, which meant that 30E got knocked of your restuarant/bar bill each night you were there, which was great and menat we could afford to eat at the slightly pricy restuarant in the hotel one night, and treat ourselves to champagne etc (we were celebrating a birthday).
We liked the gym and wellness centre, which has a plunge pool, sauna and steam room, and is great to use in the winter when it is so cold outside. They suggest you don't wear swimwear, which I wasnt too comfy with, but we were alone in there, so that was ok!
It is in a great location, with the Kurfurstendamm U that takes you across into East Berlin right outside, and the Zoo S-Bahn a 5 minute walk away, and loads of shops and sights on your doorstep.
It is in a busy shopping district, but still has lots of smaller quieter streets around so you can find cosy bars and restuarants for a drink in the evening or food in the day.
