First of all, you will be dealing with a wonderful woman named Marcia. She is fantastic from A-to-Z! She is a great communicator, she is extremely helpful, and she takes extra steps to be even more helpful.
Here are the good points about the apartment: it is very close to so many places that you will want to see and visit. It is a block away from Rua Santa Catarina, which is parallel to the street where the apartment is. On that street you will find more restaurants and shops than you will be able to visit. You will also find the Bolhao Metro station very close by, and from there you can get to any place in Porto. The air conditioning in the apartment is fantastic, the windows are large and give you a lot of sunlight. The lift works very well. The building feels secure and it is equipped with a washing machine and a dishwasher,both of which are in very good condition. Sufficient toilet paper and paper towels, along with shower gel and hand soap, are provided. Marcia also left me some coffee and detergent for the various washing machines.
These are the less good points: while the apartment is one block away from Rua Santa Catarina, you have to walk about 260 steps from the door of the apartment to get to the street that connects the two (Rua da Firmeza, I think). It is a pleasant downhill walk, until… you have to come back, when it is uphill. Secondly, the second bedroom is accessible through a spiral staircase which is very tight. The steps are about 20 inches wide. You would not be able to bring a large suitcase to the second floor. Thirdly, the Internet did not work properly most of the time. Marcia was very good about coming out and rebooting the modem. Eventually, she found out that the whole building was having a problem with the Internet. While this was not her fault, certainly, it did take away some of the pleasure of staying there. Finally, and this is my largest concern, and I have shared it with Marcia: there is a rule in the apartment that you cannot flush used toilet paper down the toilet. Seriously. They ask that you place it in the trashcan next to the toilet. Frankly, I think this is disturbing and very unhygienic. I have never seen it done this way anywhere and I have lived in many parts of Europe as well as in southeast Asia. When you defecate and clean yourself, you should be able to get rid of the used toilet paper through the toilet. My guess is that the toilet there would be able to handle it, but I do not know, because I followed their rule, being very jealous of my good reputation as a good guest. But I would never stay in a place again with a rule like that.
So what is my final thought? If you can live with the toilet paper issue, this is a fantastic apartment.