We stayed the month at Javier's place and found it a fantastic value. It was perfectly located for our needs - very safe and away from the bustling city centre but an easy 20 minute walk put us right in the heart of Barcelona.
The rental was not exceptionally furnished, but the space had the basics down with a big comfortable pull-out couch (two singles) and the cooking tools we needed for our month there. The shower was a bit small and institutional-feeling, but the split bathroom made good use of the unique apartment shape.
While it is not lavish or fancy, the value here was just unbeatable - we would have extended our stay longer had the flat still been available.