The hosts are really sweet and thoughtful.
Easy to get everywhere by feet or by public transport - due to the central location.
The apartment has everything you might need to cook and to relax :)
There is a nice oriental market near the house, where you can buy your groceries.
Just keep in mind a few things: 4th floor (you will walk a lot of stairways in Lisboa anyway :)). Tiny shower - will be uncomfortable to use if you have a wider figure :)
The neighborhood is full of African and Indian immigrants - which is okay if you love exotic food, but nervous if you're a girl walking late at night.
Overall, Elsa and Rui's apartment is an excellent place to stay, you will love it.