Luis is a great host, very helpful, responsive and friendly who will do his best to make sure you have a great stay.
The room, beds and desks/chars are comfortable & a good size, with plenty of storage in the cupboard. The flat is clean, in good condition and comes with all the important amenities. The area feels safe and clean, yet traditional.
There a supermarket, a bank with 2 atms, many restaurants and smaller shops near the place. Public transport into town is about 10-15 minutes walk away and will take about 20+ minutes depending on where you go. The flat is in easy reach from the airport which is a plus! As others have mentioned you can hear planes, but personally I've not found this too much of an issue even with windows open.
I woul definitely recommend this to anyone who's not set on staying right down town as you get to see a nice part of Lisbon and are with a great host!