We stayed 4 days in Mar 2019 (2 families, 4 people in total).
The location of the apartment is great, 100 metres from Plaça d'Espanya. The direct view on Montjuïc is absolutely terrific.
The apartment itself is nice and clean. Full kitchen with appliances and enough room to hang out, quite convenient if you are planning to have some meals or a bite and a couple of drinks at home.
3 bedrooms with 2 single beds each are relatively small but decent for the city centre. Anyway, we did not spend too much time there.
Check-in and check-our were smooth, all communication was easy.
Overall, I guess we saved at least a half of the comparable hotel rates.
We had a great time in Barcelona including a Zurich Barcelona Marato experience.
Thanks a lot to Juan Carlos & Nina. Good luck to your business!