Located at Sao Bento station - you can not be more central in Porto city center! Everything is in walking distance (although quite steep streets). Apart from top sites, the going out area is up the hill beyond the University..
The Guesthouse is very basic: bed, bathroom build into the room (very small but working), fan, coffee machine / water boiler in the common area. My room was on the top floor with the window towards the backside, hence not so much noise as to the street / train station.
Vitor is a nice guy, running the place with his grandmother. Welcoming and supportive (e.g. a quick repair of a broken lamp)