The flat was a good size and very clean. However, it was further away from central Lisbon than we anticipated - there wasn't much to see in the neighbourhood. The metro is very expensive, which meant we relied on Uber to get us to specific places rather than being able to hop on and off the metro or bus throughout the day, so we saw a lot less of Lisbon than we would have liked. This also made it a very expensive trip. The only local supermarket was also expensive.
The main issue was safety. The flue from the boiler in the kitchen wasn't boxed in, there was a huge metal-framed glass rectangular hood above the cooker at head height which we banged our heads. The cooker was raised on a cupboard which made it very high to cook safely, and there was a problem with the wiring that was particularly worrying because there was no smoke alarm. (The toaster blew up, the kettle kept fusing and the lights came on up to half an hour after we turned the switch on.) Our host initially denied there was a problem and seemed unconcerned, although did say that she was getting an electrician to look at it after we left. It marred the end of our stay, and it did make us wonder what safety checks Airbnb does. These issues may be resolved, but future guests should check.