Highly recommended if you want a nice place to stay (they have 2 terraces!) and don't want to be in the middle of the craziness of central Lisbon. Still only 10-12 minutes away by cab (Uber/Bolt is your best choice... super cheap!) to all the best things in Lisbon all while being literally next door to LXFactory, which will be filled with music on the weekends so I also recommend grabbing a bottle of wine and just enjoying the music & views of the 25 de April Bridge.
Our host from Gem was great and met with us at the AirBnb and check-in was easy. They were quick to respond to us (the coffee machine was broken & they responded right away) and were very helpful with recommendations.
While it is on the top floor of the building, you get used to them fairly quickly so don't think you'll be out of breath every time. Definitely check this place out when looking into visiting Lisbon!