I’ll start by saying I would probably stay here again, as all in all it was good value and experience. That being said, some things I would have been glad to know in advance:
Small means SMALL. I’m 5’10” and I had to contort a little to sit on the loo, and when my 6ft long phone charger was plugged in to the far wall of the bathroom I could sit on the bed. I’m a North American clothing size 16 and the shower stall was pretty cramped. So if you’re a traveller in a bigger body there’s a real chance this could be an obstacle for you.

Scent sensitive travellers may want to chat with the owners in advance as the region favours quite scented laundry products.
There is a tiny communal kitchen where guests can grab tea, coffee, and water. This is right outside the door of this room, as is the main entrance, so if you’re a light sleeper or just don’t want to hear people definitely bring ear plugs. There is a quiet hours policy though, so it’s pretty good.
The location is great if you’re looking for proximity to tourist destinations and there are many fantastic restaurants close by.
The best feature in my opinion was the personality controlled air conditioning. It made the room so comfortable and since it’s teeny it cooled down very quickly.
If you know these things in advance, and know that a guest house is more like a private roomed hostel than a hotel, this place is going to be a great jumping off point for your stay in Barcelona!