I've just completed a week here and you'd have to be very picky to find fault.
The staff were very friendly and I was greeted in excellent English although I tried to speak German as much as possible. I was given a large room with generous facilities on the top floor, just next to the second lift (which opens onto the inner courtyard) but heard no noise throughout my entire stay. I could only find four small niggles: the mattress is embedded in a frame so that when you sit on the edge of the bed, your legs rest uncomfortably on the wood; I question the value of two single duvets on a double bed - I ended up sleeping with one across me and the other on a shelf; the television was woefully small and barely visible when lying down; and, there were only 5 hangers in the wardrobe (with two others on an open rail). My two "must-haves" were fine: the mattress itself was firm but OK, leading to a decent night's sleep, and the powerful shower was plenty warm. The maid service was excellent and everywhere was spotless.
I was mildly disappointed in that the free Wifi is limited to 256kbits/s. That's OK for emails but browsing rich-media sites was painful. You may want to pay for the upgrade.
I ate in the Bistro a couple of times and it was decent but the selection is limited (soups, salads, sandwiches, pizza). Breakfast in the room was a bonus (at €16/day) and I enjoyed the eggs and bacon particularly, while remaining sceptical about the wisdom of salami and other sausages.
This hotel is perhaps the best we've ever stayed in worldwide. Located 20 meters from Anhalter Banhof S-Bahn station, we couldn't have asked for anything better. The area is very quiet despite being situated 600 metres from Potsdamer Platz. The building is an old Siemens factory which is very spacious, clean and professional looking - whilst the outside also remains clean and tidy.
Our room (563) was an Atelier Deluxe room, and did not disappoint. A soft bed with plush pillows and duvet, a freestanding bath tub, a large TV, desk and plenty of bathroom space all featured as did complimentary bathrobes and slippers. The room was cleaned daily and replenished with clean towels on a regular basis.
We used the hotel as a base to do the sights of Berlin, as it was very centrally located, within easy reach of public transport and sufficient shopping and food outlets.
If you wanted to you could walk to most places within 30 minutes. I would recommend the Berlin welcome card as it gives you easy access to the buses, trains underground and trams, to help you get around the city as well as giving you discounts to a whole host of attractions.
There were some great views of the city from the hotel bedroom.
The parliament building is also recommended, but you will need to book in advance for your visit, which can be done online from the UK.