We loved our stay in Cat's apartment. We were greeted by Cat's husband who showed us all we needed to know about the apartment and told us about the local area. There was also a folder of helpful tips and recommendations for restaurants left in the flat which was very helpful. The flat was extremely bright and more spacious than the photos would suggest - definitely roomy for a couple and you could easily fit a family in there. The location was fantastic if you're looking for the buzz of barrio alto. The streets around the apartment seem quiet in the day but come to life at night - shutters open to reveal a multitude of restaurants, bars etc. People spill in to the streets until the early hours of the morning most nights. Given this the noise is not as bad as it could be. Though you can hear chatter etc, this certainly didn't disturb us. The apartment is walkable to all the main sights (as long as you are prepared for some hill walking) such as principe real, the mercado de San Ribeira and some lovely views of the tram.
We loved our stay and when we come back to Lisbon we will certainly be back!