I will definitely be staying here if I come back to Lisbon.
The place is walk-able in minutes to nightlife and the Timeout market. The market has a very hipster feel with new restaurants and gourmet food and drinks.
The location is good and you can walk to the city center in maybe about 20 minutes (uphill) and and is close to public lines of transportation if you aren't feeling the walk.
Oswaldo is an awesome host. He was able to accommodate my early arrival time without a problem. He is responsive to calls and messages. He even checked in after I was there to make sure things were OK and if I needed anything. Additionally he has a book of attractions, places to eat, and even routes for touring the city which is completely awesome. A big help for navigating!
He has cleaners come in and the place is very clean. I was here in January and it was a little cold, but I followed Oswaldo's directions with the heaters and I had no problems whatsoever.
Although not an issue, this place is close to some nightlife. So occasionally you might here some people walking home at night. This was not excessive. And I usually find that if you stay in good central spots in a city you will always have that. Again, not an issue or complaint but just an FYI.
All in all...HIGHLY recommend!