Apartment is as advertised - it's clean, bright, airy (with aircon - big plus), has nice views over the square outside, is ideally situated for the castle (Castelo De Sao Jorge) and nicely served by buses and trams. It definitely has the feel of a studio flat - but that's not a problem, especially if only two people are staying there. The metro is slightly further away - but a pleasant walk, and a largely downhill one.
As for inside, the sofa is big and comfortable, as is the bed and bedroom area. There is no oven but I guess most visitors will eat out most of the time. Fridge is a decent size, it has a microwave and a hob too. Bathroom has a walk in shower with lovely green tiling.
Only one minor point to flag - the apartment is up two flights of very traditional, old, steep stairs which may present some problems if you are a family with small children, are disabled or have mobility issues, or are carrying lots of luggage. Just one to bear in mind if you're deciding if this is the right place for you.
All in all, a great stay was enjoyed here, helped by day after day of lovely September weather. Hosts' check in process was in person too which was a nice touch. Would recommend to those looking for a pleasant base to explore the beautiful city of Lisbon.