Marco's place was exactly as described. It was extremely well located: brilliantly central but not too noisy. The place was clean and very well furnished.
Marco's suggestions about where to eat and what to do in Porto were all spot on. He'll steer you to all the cool places, if you ask.
Only three other things to note: firstly expect to make a bit of a climb to get to Marco's place, but that's just what the whole of Porto is generally like. Secondly, do note that the building lacks an elevator, although there are only three manageable flights of stairs to go up. And thirdly, the air conditioning in the height of summer comes in super handy.
If we ever have the good fortune of coming back to Porto, Marco's place is where we would like to stay!