I'll start with the positives on my experience.
The location was great, in Madrids center. You can pretty much walk to everything.
The apartment was clean, and it was exactly like the pictures.
Onto the negatives;
Linhuo took so long to answer. Sometimes 1-2 days.
Linhuo also said that we would be able to early check in, so we could leave our luggage in the apartment at 12, but Linhuo did not answer, until 1.30PM in which one of Linhuos staff contacted us.
The staff was helpful but could not speak a word of English, nor tried that much.