Just came back from a weekend trip to Berlin where I stayed at the Four Seasons. Happy to report that the hotel is as good as I had heard, with only one minor snag. The room was great: standard king, good size (especially for a European hotel), lanai with a view of the square and cathedrals, large TV and DVD player (DVDs available for free from the concierge), and an absolutely fantastic bathroom (marble floor and walls, separate soaking tub and shower, extremely nice)

Service was typical Four Seasons: gracious, accomodating and personalised. The one snag I mentioned: on our second night, I asked the concierge to recommend a nice steak or seafood restaurant, note: my girlfriend and I were dressed for a night out (suit, no tie for me; nice slacks and a blouse for her) he recommended a place nearby (although I mentioned that I had a car) and made us a reservation. Well, we decided to walk and arrived at the restaurant-The Block House- and were quite surprised. It was the equivalent of a Sizzler steakhouse in the States (brightly lit, plastic gingham table coverings, large circular salad bar, etc.) We hightailed it out of there and walked to the Hyatt, where we tried to eat at Vox, their upscale restaurant, but without a room in the hotel and no reservation for dinner, they wouldn't seat us. 25 minutes of walking and four restaurants later (all full), we gave up and went back to the Four Seasons for room service, then decided to cut our losses and stay in the rest of the night.
Overall, I would highly recommend the hotel, just be sure to get a second opinion on the concierge's choice of eateries.