This is a great space, especially if you're on a budget. The room is simple with basic furniture, but immaculately clean and quite comfortable; there's plenty of storage and a really nice view of the treetops from the balcony. Just about all the major tourist destinations are easily walkable--Sagrada Familia, the Plaza de Catalunya, Casa Pedrerea and Casa Batallo are all about 5-15 minutes away, with las Ramblas, the Barrio Gotic, and El Raval about 10 minutes beyond that. The neighborhood has all the extras you might need on a trip--a small market across the street that's open until midnight for water or snacks, a cafe on the corner for breakfast, any number of very good restaurants within walking distance, and an ATM two blocks away that didn't charge a conversion fee.
A few things to be aware of: it's an exterior room with a view of the street, which means it can get a little noisy (even at night). There is no air conditioning, which shouldn't be a problem--you catch breezes in the evening which keeps things temperate (unless you arrive in the middle of Europe's worst ever heat wave as I did, but that's hardly Ernesto's fault.) None of this is really unusual in Spain, in my experience, so if those are necessities for you, take that into consideration.
I didn't really interact with Ernesto, but his mother oversees the Airbnb rooms. She's friendly and extremely helpful--even helping with my laundry, which goes far and above what a host should be doing. There are about 4 rooms with a shared bath, but I think I only had to wait for the shower once in three weeks. I would definitely recommend, especially if you're going to be in Barcelona for an extended stay.