Really good stay all in all. The flat is as seen. Location is perfect, extremely central, yet no noise from outisde. Check-in & -out is smooth through the key-box at the entrance. Space is ample even for a larger family. Amenities working fine including kitchen.
Only some smaller points that can be sub-optimal. The key-electricity-card situation can be not that convenient, since it is fused to the one pair of keys. So if someone is outside, it is either entering with that or no electricity. Not convenient for multiple couples and for a family in our experience. Also, a dishwasher would be really helpful for a family, as an improvement. And the elevator is small if you're carrying a baby or babies (and the respective stroller(s)).
But all in all, the flat is really good. We went a whole week with triplet babies and we had a great experience. Highly recommend!