Renata is the best landlord ever and her apartment was the best place I've stayed in while in Lisbon.

Renata is extremely kind, service-oriented and willing to help anytime you may need her. I had electricity issues twice and she quickly helped me solve them once with a technician and the other time with the utility company. She provides cleaning service once a week and is always making sure you have a great experience while staying at her apartment.
The apartment is very well equipped: very fast wifi, cable TV, air conditioning, washing machine, dishwasher, ... and well distributed: The room is ample, there is plenty of space to store clothes, luggage, etc and has its own bathroom. The living room is quite spacious, has 2 sofas that convert into beds if needed and there is a second full bathroom for visits.
The neighborhood is really flat, which makes it very easy to walk around. There is a Lidl right in front of the building and a pingo doce (supermarket) about two short blocks away. Corte Ingles (mall, movie theater, supermarket, etc) is just about 10 min walk away. There are several cafes and restaurants in the area and a very nice park and museum (Gulbenkian) about 2 blocks away. The building is right in the middle of 3 metro stations (Sao Sebastiao, Campo Pequeno and Saldanha) which makes it very convenient; between 7 to 10 min walk to any of them.
Seriously, it will be extremely difficult to find a better place/experience for the same quality/price ratio.