Our experience with Porto City Hosts was excellent.
Before traveling to Porto, they contacted us with all relevant information to do the self-check-in (clear steps, pictures to identify the locker for the keys, etc.). Regarding the accommodation, the apartment was great. Very cozy, clean, and complete for a couple of days with my family in Porto. It is equipped with a full kitchen (microwave, stoves, water boiler, fridge, coffee machine...), as well as a bathroom and a little inner courtyard. The location is simply perfect, we didn't need to take any public transportation for 4 days, since the apartment is located in the main center just right at the Sao Bento station.
For the check-out, they provided us with the possibility of leaving our luggage at their office, which enabled us to see the city comfortably during our last day.
To sum up, totally recommended. We will come back, for sure!