For the first two nights I had booked a room for myself without a shower or toilet. The room was fine but the shower room was waaaay down the corridor and around the corner. Wifi worked in the first room (near the reception desk) but was non-existent in the second room and very weak even in the corridors, and weak in the breakfast room. Don't depend on this for your work - it's okay for bits and pieces but that's it. Also beware: if you are travelling from now to 1st Nov 2015, there is no RE7 train from Bahnhof Zoo to the airport. The hostess recommended this to us as the quickest route, and we lost valuable time going to Zoo only to retrace our steps on the U9 through Ku'damm and requiring over an hour on that trip itself instead of up to 50 mins on the RE7 (30 mins on train and up to 20 mins wait as only three per hour). We ended up being the very very very last passengers to arrive at the airport - even the security staff were about to go off duty. We nearly were not let check in and go through security. My pleading in German and repeated compliments to the staff eventually led to our being let in. The two-month cancellation of that train is not well advertised at all, and was not on the airport website at the time I was doing all the research.
Location - safe area just around the corner from the Kurfuerstendamm and only 4 mins walk from the U-station. Entrance hallway on ground floor has great sense of grandeur. Breakfast room is beautiful - with lovely plants in the bay window. I could sit there for hours. Bedrooms have lovely high ceilings and high windows. Bathrooms have rather endearing 1970s avocado/peach sanitary ware - like a time warp! Plenty of choice for breakfast - fruit, muesli, other cereals, choice of juice, boiled eggs, plate of cheese and cold meat, choice of bread. Lovely coffee. Particularly friendly hostess. Free upgrade from room without shower to en-suite room for the second part of our stay.