The staff were very antipathetic. They would take a while to help you whenever you asked, and would act as if they were doing you a favor. Also, when I checked out early in the morning (around 4:00), a guy went to talk to me drunk, and would not quite understand what I was talking.
The hostel is amazing, you will not believe on the facilities you get for the value you pay. I highly recommend the activities organized by the staff. The guides Pablo, Harry (sorry if I wrote it wrong), Viviana and Patricia were awesome and contributed a lot for our awesome time in Madrid. Do NOT miss the pub crawl, drinking games, tapas experience and flamenco performance. For places to eat outside the hostel I recommend places full of old people, they are the "real" locals.
The only point worthy a comment I think is the fact that the kitchen does not keep up with the standards of the rest of the building. It's not a bad kitchen though, it has everything you might need from a hostel. And I really liked the fact that the shower is separated from the toilet, so if there's someone using one, it does not prevent someone else to use the other.
The staff was great. Both guys and girls from the reception were available to help with directions and stuff when needed , and willing to solve any problem we had within the hostel. The entrance to the hostel is hidden in a shopping/eating street, but besides this, the location is indeed excellent, with lots of places on walking distances. Just keep in mind that it can be really hot during the night on summer, since the hostel does not have fans or any kind of cooling system.