We had a great stay at Teresa's place. It's very central and close to underground, tramway, great restaurants etc. but still calm and quiet at night, for the rooms don't face the nice lively square it's located in.
Beds are comfy and communication with Teresa was easy and she gave us some great tips... you can feel the love she has for her city and it is contagious.
We definitely recommend the place!
Bear in mind that the flat is in a very typical and very old portuguese house with wooden floors... so there's no elevator, lock on the toilet door and you can sometimes hear the neighbors a bit, but's it's all part of the real old town Lisboa experience.