We had a wonderful stay at Javier's place. There were 5 of us (all adults), and there was more than enough space for all of us - we felt like we could fit 5 more people in the apartment! It was also great that each bedroom had it's own bathroom - it made getting ready in the morning and at night that much easier. The entire apartment was spotless.
The check-in process was super easy - Javier was super communicative before our arrival. We did miss the turn once because the apartment is flanked by narrow one way roads, but Javier was super patient and waited on the street for us. There was an included parking space in the garage below the apartment (a huge plus), but we were driving a van, so like most parking throughout our trip, it was a tight squeeze, but Javier even gave us tips on how to navigate the tight corners :)
It was one of the most thorough and comprehensive check-ins I've ever had with AirBnB - not only did Javier give us a tour of the apartment and all of the amenities (washer, dishwasher, etc.), he also gave us some great local tips of the places to see in Seville and how to get to all of them from the apartment.
The location was great - we pretty much walked everywhere from the apartment, but it was also just far enough removed from the center of all the tourist attractions that it wasn't super crowded right around the apartment.
I would wholeheartedly recommend staying at Javier's place if you're ever in Sevilla!