We‘ve had a very great stay at Sonder Barcelona. We had some organisation problems because of our flight etc. but the Sonder Team was super helpful (called a taxi for us, we could leave luggage in a luggage room and they were available 24/7). For something like a hostel, it was very clean and comfy. Additionally the rooftop bar is beautiful. Check in and out were super easy. To get to the centre of barcelona its about a 40min walk but just 15-20 min by bus/train etc.