We stayed in Joao's flat for 4 nights and had a great time. The flat itself is very spacious and comfortable, and it is very well equipped with everything you need.
The only problem we had was a leak in the bathroom, but Joao was helpful in acting quickly and the problem was resolved with a handyman ASAP.
Location-wise, the flat was good for us as it was on the same street as lots of bars and restaurants. It's only 5-10 minutes to some of the sights in the centre of Lisbon.
Joao was a great host, always communicating during our stay, and offered lots of tips before we arrived.
Highly recommended!