My fiancée and I stayed at Ricardo & Carla's apartment for 5 nights and really enjoyed our experience. The apartment is small and cozy, but perfectly acceptable for our use since we spend the majority of the time exploring the city. Since it's located in Barrio Alto, it's not "super quiet" at night but given that we live in a city, it's completely normal outdoor sounds for us. However, if you expect peace and quiet, this place isn't for you. Doesn't matter where you stay in Barrio Alto, it's going to have some degree of noise at night, so keep that in mind. I'd recommend this place to anyone who is looking for a central, fun, and convenient location to wonderful bars, restaurants, and attractions. Additionally, it's great that there's a small balcony to enjoy a glass of wine and unwind after a day of exploring the city.
We had a nice stay and would stay there again next time we're in Lisbon. Thanks for the hospitality!