If you're just staying in Porto for 1-2 nights, this would be the perfect apartment - the location is excellent and it has all the essentials.
For longer stays, especially when you have multiple people and are using both of the beds, I wouldn't recommend it for the following reasons:
1. The bedroom door is a sliding door, which means it doesn't shut out any of the noise from the living area. My friend was staying on the sofa bed and I had the bedroom, and we sleep different hours, and every sound that he made sounded like it was happening in the same room. (The bathroom door was very squeaky, which didn't help.) This made sleeping very difficult - luckily we were able to get earplugs from the pharmacy on the corner.
2. There were no cleaning materials provided. In 1-2 days, you probably won't make that much mess. But we were there for five nights, and were using the kitchen at least once a day as well as eating some snacks in the living area. By the end, we really wished we had a broom to sweep up crumbs and some spray to clean the surfaces, but there wasn't anything. There also wasn't a tea towel to dry the dishes, which meant we had to use paper towels for everything.
3. The windows don't open. There are two windows with small balconies with inner and outer doors. The right one looked like it was nailed closed, and on the left one, only the inner door opened. By day three we desperately wanted to open things up and let in some fresh air, but this wasn't an option.
Like I said, the location was great so this would be perfect for a short stay, but for longer ones this apartment gets quite uncomfortable quite quickly.