The apartment is perfect as long as you know what you are looking for. I was travelling alone, and wanted something that was accommodating but lively at night. The flat is in an area full of bars and very lively at night. Bars close at 2 am in Lisboa, so indeed it gets very noisy at night if you leave the windows opened. It’s absolutely silent and quiet if you close the windows. I was there in early September, and it was ok to sleep with windows closed (not too hot). It is in a Hill (99% of Lisbon is) and Taxis drop you off a few blocks away. As the hosts say very clearly, it’s a 3rd floor by stairs. So if you have a heavy suitcase take this into account.
Why did I find this place great? The flat is in the middle of the city. It’s very clean and comfortable for 1 person. Full of nightlife. Walking distance from Alfama, Plaza Comercio, Chiado and pretty much everything Lisbon has to offer so you can get almost everywhere walking. Also the hosts are amazing, they had some water and beers ready for me to cope with the hills and stairs!! :)