We had a very nice stay in Paulo's apartment, which is conveniently located in the Alfama district, a few minutes walk from public transportation and the Praça do Comercio. The neighborhood is pretty lively (can be noisy from the streets, but it's part of the charm of it I guess!) The apartment is clean and we very much appreciated Paulo's responsiveness to our messages before our arrival. Also, the fact that we were able to drop our luggage earlier than planned and were welcome by Paulo.
3 of us were traveling, I'd say that for more it might get a bit small but depends on your organization. For us, no problem.
All in all, a positive experience !