If location is imperative to you when travelling, Maddie's apartment is surely a top pick. You can explore the entire Baixa on foot and get to Rua Augusta or Praça do Comercio in literal minutes. The nearest bus and metro stops are also extremely close.
That aside, the place itself has got everything you may need, even for a longer stay (e.g. stoves and pots if you want to dine at home). It is relatively small but well-organized, clean and overall enjoyable.
Maddie is also extremely helpful and responsive, and the check-in/check-out procedures intuitive.
In summary, I cannot but warmly recommend this listing: give it a go if you're planning a trip to beautiful Lisbon!