Katja's place is really nice and we highly recommend to stay there. We found it very cosy and were lucky that we could use the whole apartment because Katja was on holiday. She also has hamsters that stayed in the room next door and a cat that she took with her.
The public transport is good and it doesn't take long to get to the centre. You can walk 10-15 minutes to the tunnel station Liljeholmen and from there it is only one station to hornstull where you can find many nice shops and bars as well:)