We had a great stay at Joana's. We were met by Joana's neighbour Ana, who was very welcoming, responsive to messages, and helpful in accommodating our early arrival and late departure times.
The flat itself was nicely decorated, and equipped with all the standard amenities. It's conveniently located in a non-touristy part of town, but within walking distance of all the sights of central Lisbon, bars and restaurants (and a nice local restaurant just down the steps outside!). There's also a nice terrace with views over to Graça.
The only issue we had is that the walls are on the thin side. We also got unlucky with the neighbours making a lot of noise a couple of days in a row, which woke us up one morning. But overall, a very nice stay!