My girlfriend and I stayed in Tiago's apartment for a week and it was a great experience. The apartment is located in bohemian neighborhood of Lisbon old town where it's packed with nice bars and restaurants and it's famous because of it's nightlife. Most of the attractions in the city are in your walking distance, yet it's still close to the main street if you want to take a taxi or Uber (btw uber is amazingly cheap in Lisbon!).
The apartment is located in the first floor with some steep stairs (shouldn't be a problem unless you have big luggages), it's small but spacious enough for 2-3 persons, equipped with all the things you might need during your stay, the bed was also comfortable. As mentioned, the neighbourhood can be very busy at night but the bedroom is located not next to the street which minimize the noise (unless you're too sensitive to noise).
If you're travelling in the colder time of the year, be prepared that apparently many houses in Lisbon do not have heating system except portable electric heaters.
In general I would recommend Tigao's apartment as it's a great place to stay in the beautiful city of Lisbon! :)