We liked Melvin's apartment most of all for it's location. You can go everywhere walking and the street where it's located it's really quite (despite being close to a central area).
The online big problem was the wifi. He told us as soon as we arrived that it wasn't working and that he'll try to fix it, but it wasn't possible. Being tourists it was our only way of communication and for work, so it was truly disappointing.
Beside that, everything else was great and I recommend this place for everyone looking to do all the touristic things in Madrid. They even let us drop our bags in their office, to keep visiting the city after check out. We really appreciated that.