We enjoyed our stay at Andreia's place over new year's eve. It is perfectly located for the metro station (a 1 minute walk from the front door) and for the Casa da Musica which we attended a concert at. There are supermarkets and lots of cafes and shops nearby.
The flat was cosy and the bed was comfortable however the kitchen is very basic if you like to cook and lacked a few essentials like a kettle and strainer! The hairdryer didn't work well so bring your own and if you are a light sleeper I would advise bring ear-plugs as the traffic from the street can be heard in the morning.
The bathroom was clean and enough for us however it could do with a bit of modernisation, we had issues with the toilet flushing and the hot water running out. The shower-head leaks a bit too but has good pressure.
We would recommend staying here for a long weekend as a base from which to explore Porto.