Javier's flat is certainly very well taken care of. It was recently renovated, and was shiny clean when we arrived.
It has plenty of appliances: washing machine, dishwasher, iron, clothes rack, kitchen utensils... The bed was great, and so were the fluffy brand new towels :) Javier was also very responsive in both checkin & checkout, even helping us with the luggage.
On the downsides, it's rather dark as it's a basement (I believe it should be stated in the description), at least in the period we were in (December). We also had issues with the heater & wifi, but Javier was very prompt in addressing those which got resolved the same day. Additionally, even if there is a lift in the building, there are some stairs to get down to the basement, which wasn't ideal for us with a baby stroller.
Other reviews hinted at a quiet stay, but the neighbors upstairs were rather noisy, with the washing machine on after 23h and frequent moving of furniture at late times.
Overall, a 4 star stay for us, but maybe we were a bit unlucky with some of these details.