Great hosts! When we had problems (our fault) with the lockbox, we called Ana in the middle of the night, she picked up, ensured that it wasn't a problem and that we're very much welcome. That impressed us!
As for the appartment, it was very, very central. As a minor convenience, there was a construction site nearby and Portuguese construction workers are loud. So use the supplied earplugs for the night. The Portuguese street singers made that up by a large margin, though. Get ready for some magical Porto experience!