Great location right in the centre of the city. 10-15 minutes walking from most tourist areas of Lisbon. Neighborhood not fancy and not necessarily quiet, old buildings, and mostly populated by immigrants but that didn't make us feel uneasy.
The apartment itself was clean, tidy and functional, but we had windows at the front, overlooking the narrow street. I am guessing the back-looking rooms would be better.
The biggest drawback was we had a problem with some drainage smell which was probably known to the owners as they supposedly sent someone to fix it, but it didn't feel any different for us afterwards.
Small advice, if you're staying for more than a couple of days probably get your own toiletries as the shampoo/body-wash was super basic, plus if we understood correctly the laundry service for an extra charge is the way to change linens.