We stayed for 5 nights at Gabriel's appartment. We had a very nice stay, Lisbon is a beautiful city. Gabriel was a great host, he was very friendly, answered all our questions and was always available via phone if we had any questions during our stay.
The location of the appartment is wonderful and easy to reach via metro if you're coming from the airport.
There were only two minor inconveniences about the flat. The mattress was rather hard to sleep on (but you get used to it). Also, at night, there is quite some noise from the streets of Bairro Alto, but we had no trouble falling asleep through the noise.

So, overall, we had a very nice stay at Gabriel's appartment !