The location is the best. You can't ask for a better spot, metro station 30seconds away, very central to go anywhere, we just went everywhere on foot. there's also everything you could wish for at stonethrow distance (cool latino restaurant down the building, shops 2 minutes away on foot, La Latina and Malasana are litterally around the corner...
The flat is really nicely renovated and clean. It just lacks a few essentials like bedside lamps, large mirrors, and hooks to hang towels and such. It's also a bummer there weren't two sets of keys for a flat that can welcome 8 people, we were 5 and we often found ourselves overcomplicating things to accomodate the fact we had one set of keys.
The last hicup was the fact that the two single beds matresses were apparently not as good as those of the the main bedrooms.
Overall i think it's a great, elegant and clean flat, and an optimal location. I just wished for that money that the essentials would be taken care of, but it didn't prevent us from thoroughly enjoying our stay and we would happily recommend it for any group of people!