This is a great apartment for the right person. Unrivalled views over the city and to the sea, very large well equipped kitchen, obviously originally a "designed" space, and worth the money. Antonio communicated well and was there on time to meet me.
I like the location, it's slightly outside the touristy bit, but near enough to just walk in (and two metro stops really close if you're really lazy). There's an amazing graveyard right opposite, not one of the biggest two but one of the best I've seen. Lots of cheap local food shops, and local places to eat cheaply too. Cinema Trindade isn't so far, and there is a great street of antique/junk shops too.
Downsides? Well to get the best views, you have to be on a bit of a hill :-). Some people may also not live the complex stairs, which are pretty gloomy. Not a factor for me, I'd probably stay there again if I returned to Porto.