We stayed at this apartment for 3 nights. We absolutely loved the place. The view in the morning is spectacular, the apartment is modern and Mariana's recommendations are spot on both for food and things to see.
Some of the reviews mention the walk to the city; they are accurate. Staying there probably adds 20 minutes each way, but it's on a nice board walk that's well lit throughout the night (we walked home around 2-3am both nights). Porto is definitely a city that starts to feel very manageable once you get your bearings.