Our stay at Gem‘s was a very pleasant experience. It is located as central as possible, in between rossio and placa de comercio- though it‘s not on the busy street. The metro, bakeries, restaurants, supermarkets.... everything is next door.
The apartment itself was really beautiful and comfy. It was decorated nicely- pretty close to the pictures. The only blemish is that the bathrooms are very, very small (you can barely brush your teeth together- therefore quite disadvantageous for claustrophobic people)
But all in all would definitely recommend it to everyone else! :)