I did a 6-week stay at Margarita and Manel's place and it was absolutely wonderful.
The unit is much better stocked than most AirBnbs and the location is about as good as it gets – super accessible to key touristy locations without being touristy itself. You also have the beach a 10- min bike ride away and lovely nature a 10-min walk away at Montjuïc.
Additionally, unlike many Barcelona apartments, it gets hours of direct sunlight. You can even sunbathe from within the apartment!
I did have one mechanical problem with an appliance and Manel was extremely helpful and responsive.