Absolutely fantastic location in the heart of Malasaña! I spent 9 nights, and it was wonderful to open the double doors to the balconies and let in fresh air and sunshine all day. In person, the apartment looks as it does in the pictures (yes, the bathroom is a bit small, and there are a lot of stairs, but these weren't drawbacks for me). Street noise while sleeping is pretty minimal given that the bedroom is toward the back and has no windows. Communication with the hosts was super quick and helpful.
This place was pretty great, but a few things could have been better. Cleanliness was an issue, particularly floors and surfaces (lots of hair on the bathroom floor and some even in the bed, bathroom surfaces did not appear to have been wiped down, etc.). I ended up cleaning the place myself when I arrived instead of asking the hosts for a reclean because I didn't want anyone coming inside the apartment during my stay and increasing my risk of Covid. Also, the entrance door to the building was frequently unlocked, which didn't give me the best feeling about safety. Lastly, although there is no street noise in the bedroom, there is considerable noise from the neighboring apartment. Maybe it's another Airbnb, but there was basically partying go on all night (until ~6am) whenever someone was there, and I got to hear all of it (including the vomiting).
Overall, I would stay here again despite some drawbacks mainly because the location is so perfect and the hosts are very responsive.