Aitor is a really nice and incredibly helpful host. He always answered quickly and made sure everything was fine for me. He also made it possible for me to "check-in" earlier. Everything you could wish for!
The flat is situated perfectly just next to public transport and it is easily possible to walk into the casco viejo, to the river and along the river to spots like the Guggenheim museum and so on.
I think for some it might be interesting to know that your room doesn't have a window. In case you want to spend a lot of time "at home" it might be a bit uncomfortable - but as I think you're also invited to use the cosy living room. Another thing might be the fact that the walls are very thin and you can nearly hear everything which is going on next doors - but with some ear plugs I could sleep perfectly :-)
To sum up, from my point of view Aitor's place is nice for spending some nights in order to explore the city...And Aitor is a very nice host. I'd go there again.