Mario's apartment is right in the middle of one of the liveliest parts of the old town, hence it is a very noisy area. If you like to party all night then this is definitely the place for you. The weather was extremely hot (around 40C) whilst we were there and we found it very hard to sleep as we had to shut the windows to keep the noise out. Some electric fans in the bedooms would help. The facilities are reasonable, especially the kitchen and living/dining area but again, even with the industrial strength fan on up there on the top floor, it was still stifling. I would perhaps recommend coming to Lisbon in the Spring or Autumn if you intend to stay in an apartment with no aircon. I do come from a cold climate though, so perhaps others may find it ok.
There are two long, steep flights of stairs up to the apartment and no lift so this place is not for the elderly or disabled. Security was excellent.
To summarise: this apartment would definitely suit younger people out to enjoy the nightlife as it is right outside the door.