Check in was a bit of a hassle. We never received the mandatory checkin email, which required chatting with hotels.com to resolve the issue. We tried to call the smartflats people after receiving the number from hotels.com (the one on the website is disconnected) directly and were put on hold (while we were chatting with hotels.com) and after 15 minutes of being on hold, we hung up. The checkin also requires a photo id scan from your phone as well as an additional $$ euro deposit before they will give you the access codes.
Just expect some hassles trying to check yourself in.
Also, they’re doing MAJOR construction directly across the street, which resulted in a 7:30 wake up call of pneumatic drills followed by the sound of falling bricks. This continued throughout the day. It was however tolerable.
The flat did come with a small washing machine—a definite plus—but no dryer nor clothesline/pins to hang up things to dry afterward. We made due by hanging things from open windows and the radiator.
Finally, the coffee maker uses little custom espresso sachets, and they only give you a couple for the entire stay. If you like making coffee in your room in the morning, best to bring your own instant. There was an electric kettle.
The room itself is quite comfortable and a good location.