We stayed at the Adagio in November for four nights and had a great experience. It was our second visit to this hotel, after a nice week a year ago.
The hotel is located in Berlin west, one block from Kurfurstendamm, and close to the U-Bahn. Berlin is huge, and the hotel looks far from the eastern sightseeing spots, but I guarantee that it's perfectly located for people willing to use public transportation.

The rooms are actually studio apartments, clean and comfortable, with all the amenities needed. The staff was cordial and helpful. When you stay more than three nights, rates become really interesting. I would stay there again with no hesitation.

My family of four stayed three nights in this hotel at the end of September and were pleasantly surprise with the modern room which felt new. Our room was apartment style, complete with a kitchenette and separate room with a queen size bed and plenty fo room. The kids loved this hotel.
Considering the kitchen facilities, we opted not to have breakfast, but to buy our own supplies from the supermarket across the street. Bear in mind, should you arrive on a Sunday, as we did, the shops will not be open and the gas station on the corner did not have breakfast supplies, so we ate in the hotel and paid the hefty breakfast price on the first day, which I didn't find to be good value for money, but our oversight really.
There is free internet in the lobby, which we found convenient to use, and a coin-operated laundry for guests. However, arriving on a Sunday proved difficult, becasue the reception staff were out of change, and the gas station would not give us any either - bit frustrating. The laundry was such an appreciated service, but it would have been better had it been a token operated service as we found in other hotels, which would have taken the stress out of finding and keeping the correct amount and number of coins required.
The front desk staff were good, although the language barrier was difficult at times, we were relieved when there was a good English speaker on the desk, as this was our fist time in Germany and our skills, though we tried, were bad.Overall, the reception staff we as helpful as they could be.
Otherwise, the hotel is well located from the U-bahn and S-bahn making it easy to access points of interest. Train tickets can be bought at the station itself. You can even hire a bicycle from outside the main entrance if you are game.
There is no restaurant in the Adagio, but plenty to be found close-by, the reception staff did provide us with some delivery menus for when we were too tired to go out again after a big day. That said, there was a great Italian restaurant near by- Capone's - which was just fabulous and seemed busy and popular. Great and friendly staff who paid particular attention to the children and tried to get a giggle out of them and who were very accommodating and forgiving of our very bad German.

We spent three days at Adagio Kurfürstendam. Up to three days implies normal hotel service. Free internet (ethernet cable at the roolm, wi-fi in the lobby). The room was clean and in a verry good standad, well equipped kitchenette suitable for breakfast, coffee sandwiches and a quick lunch (micro wave oven). 7 minutes walk to the U-Bahn, good restaurants inside 10 minuttes walk. Good service. We enjoyed the stay.

Berlin is a big city and it is important to choose a hotel in an area suitable for your needs. Located in the western part of the city, it is maybe not ideal for sightseeing, but when willing to take the subway other parts of the city can be reached easily, too.
The hotel itself is a very modern hotel with comfortable rooms, good breakfast and a friendly staff.