We were in Berlin for four days, doing a Rick Steves city tour, visiting museums, Checkpoint Charlie, and the amazing KaDeWe.
Location: the hotel is very close to the train station and only a few minutes walk from a Lidl grocery store. And it's only about 100 m from the Spree river.
Staff: the reception desk people were very knowledgeable and helpful and fluent in English.
Luggage storage: We were able to store our luggage at the hotel after we checked out so we could have another day of touring without lugging it around.
Breakfast: I can't talk about it because we skipped the very expensive hotel breakfast (22€ each) and ate our own snacks and groceries instead.
Fitness center: I had to get my room key coded to allow access to the fitness center. (If you know you'll use it, they can add that access during check-in.)
Elevator/stairs: one of the three elevators wasn't working while we were there. The main staircase connects floors -1 to 1-9. There's a way to use stairs to get to floor 0 too.
View: Nope. From our room, we could just see the building across the street.
Air conditioning: worked like a charm.