We loved Raquel & Rogerio's apartment in Porto! Don't let the slightly scruffy look of the neighborhood put you off. R & R have done a wonderful job with their apartment, it's stylish, spiffy clean, and the location... literally two blocks from the river... deserves 10 stars! Raquel met us when we arrived and kindly told us all about the sites she recommended. It's so great to hear the opinion of someone who actually lives in a place! :-)
The only downside, which we've since learned (after two weeks in Portugal) is unfortunately common throughout the country, is endlessly barking dogs! We had a bit of a break while trekking through the Douro Valley but our time in Madeira was almost torturous with the incessant noise. Anyway, certainly not R & R's fault, just a heads-up to other travelers.
Oh, there is a bit of a climb up to the flat (no lift available) but it's not terrible. It will help get you in shape for all the hill-climbing you'll do here!
Highly recommend Raquel & Rogerio's place in Porto!