Good location and very clean apartment. Only downside is that it is not really furnished with much, it's a very plain apartment. This might not be a factor for some people but something as simple as not having pillows on the couch or the lack of decor can make staying there for a long time a bit of a downer. There were also some Wi-Fi issues that I had to message the host about. The router can't be seen from within the apartment, so for people looking to stay there and work remotely, just know there might be spotty connection from anywhere within the apartment and not great speeds. The last issue we had was the hallway lights; they would automatically turn on due to some movement sensors, and were not controllable with a switch or dimmer. This meant that if you got up in the middle of the night to use the restroom, you'd be met with super bright lights that turn on the moment you step out of your room. Some small inconveniences really, but added up can make you notice them.
Other than those issues it's a very spacious apartment, was extremely clean when we arrived, had very nice bathrooms and showers, and was truly in a great location within Gamla Stan. I'd recommend this place for large groups or families that are doing short stays, but maybe not for people who are choosing to work remotely.