We stayed at the flat for 5 nights with our toddler and in general had a really nice time. We loved the location as it was 1 minute to the beach which was great with young children, as well as being really quick to town and the Aquarium. We visited Mont Igueldo, did a boat trip, the playgrounds are great, spent lots of time and the beach and having Pintxos in town.
The flat is spacious and the lift was helpful with the pushchair and suitcases. The agent was responsive as we did have a few issues and accommodating to a slightly earlier check in. With a bit of maintenance the flat could be greatly improved as things are starting to get a bit worse for wear in places. Light sleepers may need a white noise machine as even with windows closed you hear traffic noise and noise from neighbours, which is common in flats but useful for visitors to know.
It is worth the money but would be amazing with a few improvements.