One thing to note is that the ceilings are very low. To comfortably live in the apartment, you need to be under 160CM. Anything more will be very uncomfortable for you. You will constantly bump into things, ceilings, head beams etc.
Also the bathroom is very small with the shower being very tiny!
Finally, if you want a quiet nights sleep, you wouldn't really get it here. Alfama is quite an old part of town so you do have quite a few noisy neighbours including crying children, chirping parrots and a barking dog.
Location-wise it is great and the hosts were amazing, but don't expect a comfortable stay while in the AirBnB.