This place was great! Very new apartment, very clean, and spacious. It had 2 bedrooms (one with a full size bed, and one with 2 twin beds that could be pushed together to make a queen). I think the sofa in the kitchen may have been a pull-out. Two bathrooms with very nice showers for Europe. The unit is on the 2nd floor and there is no elevator - but Luis helped us carry in and out our luggage. :)
It is about a 10 minute walk from the Sao Bento train station, which would be very easy usually, but a bit hard uphill with luggage :). The location is right in the thick of things and there is a very cute breakfast spot right nextdoor - Hungry Biker. You can walk to anywhere in the old town from this place. The neighborhood felt very safe and we slept with our windows open both nights.
Luis arranged a driver to take us to the airport and it was much easier than trying to find a cab on cobblestone, hilly streets with luggage. I would recommend arranging that though the host if you're coming from the airport. It was 25 Euros cash - which he said was about the same price a cab would cost.
The only thing to note is that it was a bit noisy in the morning. A neighbor was playing the radio very loudly out her window, but if you close the windows it's no problem.
I would definitely stay here again and recommend it to anyone going to Porto.