We really enjoyed our stay here in June. The location is pretty much perfect, right near the Santa Justa elevator, and it was always great to step out in the morning and be right in the middle of things right near Rue Augusta. Lots of transit options very close by and Uber is super inexpensive in Portugal too. Restaurants/bars do close relatively early in Baixa (~10pm) so not a lot of late night noise or activity, which could be good or bad depending on what you're looking for. There's plenty of stuff still open though in nearby Bairro Alto for late night activities which is a very short (though quite uphill) walk away. Also relatedly, it's always nice to walk downhill at the end of the day to get to the airbnb since it's in the valley.
The apartment itself is incredibly nice and very well thought out. Very modern décor, comfortable bed, and plenty of space for two. The sound proofing was incredibly good, I was very impressed and shutters keep out the light very well. AC worked well even as Lisbon was going through a heat wave. Balcony is quite narrow but gives some spectacular views of the elevator and there's enough room for a small chair and table like in the photos so had wine in the evenings a few times on there which was so nice. The combo washer/dryer worked great and iron worked well. Elevator was quick.
Overall I'd highly recommend it. Definitely one of the best Airbnbs I've stayed in, great location, and very happy we stayed here.