The apartment is in a great location, just a few minutes from Rossio. The street has excellent local restaurants as well. We literally ate at all the restaurants along the street instead of going anywhere else. Great fish dishes! We felt safe the entire time, although you might see some locals "doing some business".
The apartment (#3) is on top level, and the stairs leading up to the front door are very steep and narrow (no elevators) but was not an issue. It can be a great leg exercise. The entire apartment in general is clean and cozy. Full functional kitchen, terrace (both front and back), and a good size bed for 2 people.
The main issues I had with the apartment were: dirty shower curtain (doesn't look like it has been changed), tiny shower (which I don't mind if the shower curtain was changed), no bathroom ventilation, and lack of response from the host. We lost power one night, sent the host a message - no response. I also sent him 2 other messages the night before check out, no response either. Locking the front door can also be tricky so make sure to ask the host how to do it.
For the value of your money, I would still recommend it, but if you're staying longer than 2 days, find something else.