I've spent a long weekend in the apartment with three friends for a short holiday in Stockholm. For this trip, the apartment was absolutely sufficient.
It was perfectly clean and the location could not have been any better. The room itself makes most out of a small space. As one can expect in the old town, the building is a little bit crooked, so mind where the water on the bathroom floor flows. It seems as due to the natural movement of the building, one of the windows does not really close (at least in Oct/Nov), but thanks to the curtain you don't have to fear the cold from outside coming in.
Be aware that the apartment does not have a table but a bar. So if you're more than two guests, you will have problems sitting down together to eat. The kitchen equipment is fine for basic dishes.
Unfortunatly, I couldn't reach Sofi per Airbnb-chat shortly before or during our stay for smaller questions, but in general you can find everything in the descriptions and her initial message.
Overall, the apartment primarily scores with its location. It's perfectly clean and sufficiently equiped. And Stockholm is great anyway ;)