Karen's apartment is in a great location, really close to the meatmarket (so lots of great food on the doorstop), public transport (trains and buses very short walk) but it is also walking distance to the centre of Copenhagen.
Many others have noted this, but if mobility is an issue, the apartment is five flights up and the bathroom is a bit tight on space so might need to be mindful this.
Karen was a great host and greeted us upon arrival and was very speedy with communication when our flight was delayed and we were slightly later than expected. Additionally was happy to provide advice about the area.