Charlie was very friendly and the room was very well connected to the centre of the city (really close to Gran Via and Malasaña district). Our room was one of many other airbnb rooms on the same floor, so we kind of felt like being in a hostel more than in a "typical" local airbnb flat. You share the kitchen with the other guests and host as well. We had our private bathroom though, which was a comfortable thing. It was also rather cold in our room, especially because you couldnt really close the balconydoor completely (even if you did it properly as charlie showed us) and the heating was off or on very low level. As it is a little bit confusing in the description, I also want to get this right: Check-out time is on 12:00 midday/noon. We had some confusions about that, however Charlie was so kind to put our luggage in his appartment for a few hours. But afterwards he didnt show up right on time, so we nearly missed our flight - fortunately everything worked out well in the end.
So in conclusion the room is cheap and suceeds through its central location. If you're also looking for smth hostel-like, then you should go for charlie's :)