We were for 6 days in Lisbon at Isabel's apartment. The location is the best! It's central but not directly on the main street. I don't get the complains about the noise? You are in the city center, you will hear normal city noise during the day. Nights, we had no problems. It is not "strange/dangerous" neighborhood as somebody wrote.
The apartment is charming and well equipped. It is in a old building without lift. For us was no problem, but you should be aware, if you have problems going up the stairs.
And, the two best Ginjinha bar/store are right up the corner!
We had a great time and would definitely recommend staying at Isabel's.