This is an excellent choice for where to stay in Porto. Some highlights:
-Location is perfect--convenient and close to everything, yet very quiet
-The apartment has a modern heating system which actually keeps it warm, which from personal experience is not always the case in Portugal
-The kitchen is well stocked with everything you might need, including a dishwasher and even a few basic groceries that were left there by the hosts
-The hosts are very kind and welcoming. They even welcome you with a cake and Port wine! They also provide a very detailed guide, not only for the apartment, but also for the city, which makes it easy to plan your stay in Porto
-The design is very cheerful, which makes this small apartment feel cozy and bright
I should note, however, that I was running out of hot water when showering, just FYI if you like to take very long hot showers.