The location is hard to beat - it is steps away from a metro station, in an interesting neighborhood, on a street full of small restaurants, close to the castle and several cathedrals. The first stop of the iconic Tram 28 is also steps away.
The apartment is a bit hard to find, and it is easy to get lost in narrow winding streets, often consisting of nothing but stairs. They are so narrow that our phones' GPS failed to show our location accurately. The easiest way to get there that we found was to get off Martim Moniz station, walk South towards Tram 28 stop, take the escalator, then turn right onto Rua Marques Ponte de Lima. Once you reach a little plaza with a small statue, the house is below on the right.
Be warned that the apartment is TINY, especially the kitchen and the bathroom. You can only get down on the toilet sideways. You can either use the table or the kitchen sink. Two bigger electric appliances running simultaneously trip the circuit breaker. That's the price you pay for staying in old town. Given the rate and the location, that's the bargain I would take again with no hesitation.
The host was very accommodating - we were given space to store bags after the early flight, met in the apartment and had everything explained. Plenty of local tips, too.
Overall, great stay and I highly recommend it.