Unfortunately, this has been by far my worst Airbnb experience for several reasons. This review is quite long, as I wish to be as objective as possible.
To begin with a positive, the location is excellent, Marylebone is extremely central and very swanky.
The room itself is as pictured, it was clean, and the bed was comfortable; the window is clearly small, but if you just intend to sleep here this may not bother you. The room frequently smelt of cigarette smoke as neighbours smoke on their balconies. the room also often has a strange, unpleasant fishy smell; I believe this is because there is a vent to a neighbouring building near the window.
The communal areas have no windows at all, which means that in summer they get extremely hot (uninhabitably so on warm days), and as they have no ventilation they also have a constant unpleasant smell. The kitchen was also very unclean, despite a cleaner coming in once every few weeks.
The current housemates (there seems to be high turnover) are not particularly talkative or friendly, and generally keep to themselves; this is absolutely their right, however, I do find it quite disingenuous that the listing tries to sell this property by saying the housemates are a "really friendly bunch" when Ilva does not actually know them personally, as she does not live here but rather manages the property.
During my stay, there were ongoing plumbing issues that Ilva was aware of, including that one toilet and sink did not work. Several weeks after being told about this she did send a plumber. The plumber told us that he could not fix the issue as it would be too expensive; shortly after this the entire house smelt strongly of sewage and another plumber was sent on the day I moved out.
There was also a very strange incident in which a painter came to the house. When he arrived, he barged into several rooms unannounced, for much of the time he was there he wandered around in various states of undress (missing either trousers or a shirt). I thought he had left until he left he knocked on my bedroom door at 11pm to ask me a question. I was obviously unnerved to be woken up by a (very unusual) stranger at my bedroom door at night, I think many people would have felt unsafe in this circumstance. I did tell Ilva about this, and she took note, hopefully the same painter will not be used again.
Ilva was generally professional and communicative, and the check-in process was pretty smooth. To her credit, she did attempt to resolve issues I raised with her as best she could. I was a little annoyed with the frequency that her colleague texted me (between 1 and 3 times each week) to ask a question about the property, ask me to receive a delivery, or let a tradesman in. Upon check-in another colleague of Ilva asked to look at my driving licence or passport - he then photographed it without asking which I thought was unusual.
As several reviews noted, it is possible that a short stay here might be fine, especially given the location. However, the property is clearly not set up for short stays, in that check-in times are not flexible, and as the other tenants are permanent it is not particularly fair on them for a short term Airbnb to operate out of their home, when they have no say nor receive any benefit from it.