We had a great stay at Rafael's place. We were 3 guys visiting Nos Alive festival, so each one of us had his own room & bed. If you want to go in larger groups, I would say that 2x 2people +1 have no trouble getting accommodation. There is also the option to sleep on the couch if that's your thing.
Anyways, the apartment is huge, and besides A/C got everything you can whish for. Maybe one thing to mention: the location is not optimal. If you want to fall out the door and be right at the heart of Lisbon, then this might not be the place for you. But if you want to make a trip with your buddies, and are only staying in the apartment during the day for sleeping and are in the city during the night, then yes, this is definitely the place to stay!
Additionally: Rafael is a chill dude, always looking out for his guests. I can't imagine anyone not getting along with him. So from my side: great stay, would book again! ;D