We spent 10 lovely days this summer at Gundega's. The best point is the huge terrace ! We loved it :)
Gundega and her husband were very nice and took time to explain us what to see, how the city works.
The flat is well located, clean and very bright. Which is very pleasant, even if it's raining ! (Yes, we had a little rain...)
We were very lucky because we stayed while there were a food festival in the park just next to the flat.
We recommend you to stay there :) It's a nice place for a couple to stay and visit Porto.