This place is in a perfect location in Principe Real - we could walk everywhere. The flat is really well equipped, everything you need (except a kettle!) and there was even a bottle of wine there waiting for us when we arrived. Just two small things to note that I can't see in other reviews:
The neighbourhood was quite noisy over the weekend. Several times we were woken up by drunk people on the street, trying to ring the buzzer and rubbish trucks.
There isn't a proper curtain so if street light bothers you, bring an eye mask, the room is quite light at night.
The bathroom is overlooked by the neighbours with no blind, so don't expect to get too much privacy in there...
Other than that, it's the perfect place to stay in Lisbon. Really clean, great location, easy check-in and stylish flat.