I stayed at Rita & Miguel's while visiting Lisbon for the first time. Their apartment is centrally located, within a ~20 min walk for most points of interest in downtown Lisbon, and with good access to the metro.
Hosts were very responsive to questions, and even prepared an excellent guidebook to the city, which made trip planning extra easy. Certainly identified lots of spots I would have missed otherwise.
The apartment itself was clean and modern. Would highly recommend.