We had really good stay (5days) in Porto at Mario's flat. Location was super central Porto. We walked everywhere from flat. There were so many amenities near by flat so easy to get lunch and dinner too.
There were mid-night heavy noise from upstair and downstair neighbors weekdays and weekend. I think the wall is thin because of old building structure. Also the electric fuse went off when we tried to cook, kindly Mario explained to us what to do as soon as he heard from us.
Wonderful stay in porto, I would recommend if you want to stay in centre!