Really good location, 5 mins walk away to Trinidade station, and within walking distance of all of the main attractions in Porto. 15-20 mins walk to the river.
Marta was a great host, replies to all messages extremely promptly, mostly within a few minutes! She picked us up in her car from the metro station and took us on a tour around Porto, and spent at least 30 minutes pointing out the local cafes, supermarkets, main walking streets and attractions.
The flat was a little cold, and we had to put an extra blanket on the bed, but there was plenty of extra bedding in the cupboard. The place was very clean, with excellent wifi, and Marta even provided an extra portable wifi dongle for us to use whilst we were out exploring - amazing! There was some fresh fruit and a small bottle of port waiting of us in the flat also. The bathroom was clean, with a good shower, and lots of large fluffy fresh towels on a heated towel rack.
The only bad thing (and we found this in Lisbon as well - maybe its a Portuguese thing?) was that it was a little noisy at night. Maybe it's because the windows are all single-glazing, so didn't keep out noise very well. But a pair of ear plugs would probably solve the problem!
All in all, a great stay at a good price!