We found Mario's modern apartment to be exactly as described and pictured. It was well-equipped and most of all, it was quiet so we slept very well. The mattresses were comfortable and we had all the conveniences we could want. It was reassuring that a neighbor (who checked us in) was always there if we needed anything.
The bathroom was perfect, although we had to be judicious with the hot water (there were two of us). We also did two loads of laundry and that went flawlessly.
We found the location to be ideal as there are many good restaurants just down the hill in the neighborhood across from Sao Bento, the local train station. Plus the subway station is no more than two minutes from the apartment. We are already looking forward to our next visit to Porto and staying with Mario again.