Flat is simple and small, but functional. It's well located, properly equipped, and fairly clean. And bed is comfortable. A bit dark indeed but who cares, the idea is not to stay a whole day in it when there's so much to visit around, so it's not a problem.
Unlike some comments I could read, it was absolutely quiet during my stay, but it may depends on the current neighbourhood.
Instructions for key restitution was a bit confusing, but no doubt that it will be fixed soon. In any event customer support is very reactive :)