We stayed in Karin and Jonas's lovely apartment in Sodermalm in the middle of August.
The apartment is 4th floor (with a lift!) and is very spacious with a fun quirky retro feel to the furnishings. We were surprised to have so much room as we had heard that Stockholm apartments tend to be pretty small.
The area is great, with lots of bars cafes restaurants and shopping within a short walk , and public transport very close, bus and T Bana.
Unfortunately we didn't meet Karin, but her partner Jonas met us in the apartment and gave us lots of useful information about the area.
All in all we would highly recommend this apartment if you are visiting Stockholm.