This is a simple, no-frills place to stay, it's basically fine. The house is nice and cool inside, the flat is clean, the location close to Santa Apolónia railway and metro station is very convenient, and the city centre is easily walking distance, through the charming Alfama streets. The roof terrace you can climb to on a set of stairs is also nice with its citrus trees and comfy seats.
The host communicated readily about checkin and checkout via the airbnb chat, though it caused me a bit of confusion at first that initially the communication was in French, even though I had stated in my booking what languages I spoke and French was not one of them. I also met the host in person one morning and the host made a kind suggestion about a nice flea market nearby. Clearly a very nice person.
However, there were a few issues. Here are my words of warning: first, there was no warm water in the shower. No matter how I turned it, it was always the same temperature. I didn't see this as a big issue because each day I arrived home feeling quite hot and sweaty, and the cold water was a welcome relief, even if it took a few seconds of getting used to. (Maybe there is a trick to turning a boiler on or similar, but the host never made me aware of this.)
Similarly, there was no readily accessible wifi network, at least the host made no attempt to share a password or anything similar. Third, my room, the one facing the street, had a couple of issues: one is that the blinds kept getting stuck when I pulled them down, but I managed to solve this after I realized what they were stuck on. Second, the noise from the street is pretty loud even in the night - there is a surprising amount of traffic, and especially the great heaving, groaning sound of the buses resounds loud and clear through the sliding window (which opens onto a teensy balcony.)
I was mostly alright with this as I expected nothing fancy but I think guests should be aware of these things.
If you are a light sleeper, sensitive to noise, or you need hot water for your showers, this may not be for you. Otherwise go ahead.