Marilia's place is very well-located: exactly in the center of Porto, near all the nightlife spots and restaurants etc
The apartment is a nice studio apartment: roomy, with a kitchenette, etc., and is well-stocked and relatively comfortable.
Generally I really enjoyed my visit. There are two things that bothered me and that other guests should know
1. starting 11AM or so every day, you can hear music continuously playing. This is likely from the shops downstairs. It's not high-volume, but if you're trying to take a nap, it might bother you. (FWIW, the music is pretty good.)
2. The listing advertises a "dedicated workspace". but in reality, the workspace is a couple of stools, and a small-ish plastic coffee table. It's not actually comfortable to work in. In general, the furniture was a bit low-end, and in my stay there I was constantly wishing the furniture was better.
Other than those two things, I had a really great time, and would very much recommend the apartment.