I spent 4 night at Carlos' apartment at the end of July-beginning of August. The room itself is pretty tiny, but I only needed a place to sleep, so that was ok. The bed was very comfortable, hot water in the shower. And the breakfast! Carlos made very tasty breakfast and I had an opportunity to try different Spanish dishes (like gaspacho and Spanish-style omlet). Carlos was very helpful in terms of getting around the city. And he even took the trouble of helping me with my luggage to the Airbus stop.
The apartment itself is very nice and a walking distance from La Ramblas, Plaza Catalunya, and just a block away from the metro.
Overall, I would recommend to stay at Carlos' for anyone who wants a place near many attractions and with a good breakfast.