My recommendation is: if you're coming to Lisbon, you should do everything you can - even to the point of changing the dates of your stay - to have the opportunity to stay in Diana's place.
First of all, it's perfectly located between Bairro Alto/Chiado and Baixa, with dozens of excellent restaurants within a few blocks. Theaters, stores, historic churches and squares are also just a few blocks away. Trendy bars and clubs are slightly more distant - - close enough for visiting and far enough so as not to be bothersome!
The apartment is in a great modern building with an elevator. The sofa in the LR and the bed in the bedroom are comfortable; there's even a rug in the LR - - which is unusual in vacation rental apartments in Europe! The bath-and-a-half are attractive and fully-functional with ample hot water and sufficient shelf space to put soaps and toiletries. The eat-in kitchen (with a dishwasher, stove, oven and microwave) is well-equipped with dinnerware, pots and pans, and even some staples. There's a coffee machine for those who don't want to go out in the morning. Also unusual for European apartments, there's more than enough closet and drawer space. The LR window lets in lots of light but there are privacy shades; ditto in the bedroom except that window actually has shutters that darken the room completely.
We visited in March so obviously we didn't try the air conditioning, but with the heat on during the cooler weather (radiators in the LR and the bedroom, and radiator/towel warmers in both bathrooms) we were completely comfortable. Even so, Diana had thoughtfully provided extra blankets and a few coverlets. We stayed for a long time (more than three weeks) and Diana was happy to change out the bedding linens and towels midway during our stay. For people staying for even longer periods, there is a neighbor, Concepsão/São, who will come in and clean for a very reasonable fee; São will also do laundry (including pick up and return) for those who don't want to do their own using the excellent machine in the kitchen.
Upon arrival we were welcomed by Jorge, who also drove us from and ultimately back to the airport, with a bottle of wine. He fully explained how everything in the apartment works (European appliances can be a bit tricky!) and gave us his phone number in case of questions. Jorge also served as our driver and informative guide on a wonderful day trip to Sintra and Ericeira. He charges the same price as the larger touring companies but you're in a car and not a bus or SUV, and you're dropped off and picked up at the door to any site you visit.
Bottom line: Diana, Jorge and São are wonderful people and the apartment is the perfect place to stay during a short - or long - visit to Lisbon. We hope it will be available next year when we will certainly be returning.