The pictures are a good depiction of the property. It is clean, and the bathroom has nice water pressure.
This apartment is a good stay for one night. It's not really set up for more than that. The supplies are inadequate for serious cooking or living. The property is an awkward distance from the old town. It feels too short to drive, but it's over a 20 minute walk uphill. It could be appropriate for someone with a car, but parking around the apartment and in the old town is not easy.
The vibe is also a little off. It lacks the personalization of many Airbnbs, and the whole thing feels a bit corporate. This small building is all vacation rentals, so the people change every day. There are also people above and below and beside, so you feel like you're part of their conversations. It feels run by a property management company rather than an owner, so the people you communicate all seem to change but don't feel able to make decisions or address resident concerns. They are all polite, in the way employees at a hotel all feel polite but unempowered.
On the plus side, there is a great cafe across the street that is one of better places in Sintra to try the famous queijada and travesseiro pastries.