The apartment is beautifully located with a great view from the windows of Lisbon's rooftops; the neighbourhood is safe and interesting, lots of little alcoves to explore and tiny eateries to grab a bite at. One huge drawback is that the street that it's on is on an extreme incline, so no taxi drivers will go up, meaning that if you have heavy luggage, it is supremely unsafe to lug it up or down. Pack light and wear good shoes!
Check-in was confusing because it's run by a company, so there were some communication issues between 2 people (we were told that check-in was at 3pm, but then another representative said that she was going to be there at "13h", so we thought 1pm was perfect for us, but it was presumably a typo because she got paggro assuming that we wanted to check in early for free. Not the case, but make sure you're aware and double check timings with them for clarity's sake). They were also oddly evasive about luggage storage; to set the record straight, it is not provided by them, but they can recommend some paid facilities.
The interior is lovely and homely, well-decorated, with a comfortable living area and well-appointed kitchen and TV with Netflix, which was a great convenience. I wish the bed linen, throws and covers were cleaner, but it was acceptable. We slept well because the surroundings were very quiet, which was greatly appreciated given its proximity to so many places. All areas have dual air-conditioning, which was really nice. There was also a good working washer, and a clothes rack was provided, which we appreciated very much. Showers were wonderful and strong with endless hot water, which really elevated our overall experience. The master bathroom had no sink space for toiletries, so make sure you're prepared for that.
All in all, great value for an apartment in that location, and suitable for a family or a group of friends.