My colleagues and I stayed at Bela E Rui's place for almost a week during the Web Summit 2018 and it was amazing. The beds are comfortable and the fact that there was hot water available all the time was an added bonus. There was also pasteis de nata and beer for each one of us at the apartment, which was a sweet added bonus (even though we didn't drink the beer :) We felt really welcome.
The apartment is located near a Verde metro line, so it was easy to go downtown to relax and see Lisbon.
The only one thing you should take into account that wasn't ideal is that there's no elevator and the apartment is on the third floor (so in case you have suitcases, you'd have to haul them up and down the stairs). It didn't really bother us since we had to do it only in the very beginning and when we were leaving, but it's something that might be more of a challenge for some.