I spent a month at Rita's apartment, and had a very good experience overall. Check-in went smoothly, and everything was very clean.
First of all, I really liked the neighbourhood. Narvarte is a nice and conveniently located area that's just a little bit away from the usual tourist/foreigner spots. The apartment is right off of Obrero Mundial, which is a fairly busy street, but it's a friendly, safe and convenient neighbourhood. You also get some nice food options nearby (try homestyle breakfast at La Cocina de Rosy, a little hole-in-the-wall place with no sign [at the time of writing] just after La Foto Cafe on Obrero Mundial - and tell them Roman sent you!). Being a short walk from Parque Delta mall is great, too.
The building doesn't have good soundproofing, so sound carries easily, but luckily the neighbours tended to be very quiet. You don't get any road noise because it's on the inside of the building, and the inner patio does let in a decent amount of natural light.
The amenities are a little bit unique - A pair of bunk beds and a mattress that's just off the floor on rollers, but no regular bed with a bedframe. It's also a little cluttered, but extremely well-equipped - it was great to have a stove, fridge, blender, microwave, coffee maker, toaster oven(!), and dehumifier(!!). The bathroom was in good condition, but very small - you might find your knees against the wall when you're sitting. Wifi was fast and reliable. And finally, Rita was an excellent host - she was very responsive, and patient about answering my many questions. Overall, I'd recommend it if you want to stay in Narvarte (or near La Roma) and are on a budget (since it was very affordable when I booked it).