We, stayed at the hotel early November for an extended weekend getaway. The hotel staff eased our way with a very smooth ez in / out process. Room is very big even in American standards. Bathroom has separation between the basin (two of them) shower, bath and stall area and has a lot of light. Extra towels and soap as a standard would have been nice. Room was very clean. Free WiFi worked well all around this big hotel. SPA area is nice and is open at extended hours. Be careful of what seems to be a Jacuzzi.....it is not, and the water there is very cold :-) the hotel is centrally located, but as Berlin is a large city, make sure that the location is good for you on the west side of town.
Here is a tip - if you book on-line, register and receive a free breakfast which is valued at 16 Euro / person / day ! The breakfast buffet is grand and on top of the huge selection you can ask for omelets, pancakes or crepes to me freshly made for you :-)
Berlin has a lot of great variety of hotels to offer, and the Concord in located high on the list, and rightfully so.