The good:
A really handy location a short walk from Trindade metro station.
An easy downhill walk to the river and some of the main tourist attractions.
A great selection of cafés and bars nearby.
The hosting company provided us with some recommendations of places to check out during our stay in Porto. And when we couldn't work out how to use the oven, they sent someone round to help us out.
Decent wifi.
The bad:
The host's representative was a little late meeting us at the apartment. Not a big deal, but it did mean we had to go and get a coffee with all of our luggage while waiting for them to arrive.
Some of the fixtures and fittings were not of a very high standard, for example loose door handles and light fixtures.
There was an issue with water leaking from the ceiling, however this seemed to have been caused by the apartment upstairs having a plumbing issue, so not the host's fault.
The biggest problem, though, was that the windows didn't close/lock properly. The apartment is on the fourth floor, and this seemed like a pretty big safety issue. For this reason, I would recommend checking that the windows have been fixed if you're planning to stay here with children.