My wife and I spent 6 nights in the apartment in December. The apartment is in a great location, we walked everywhere, except taking an Uber to Belem.
As noted the apartment is on the 4th floor with no elevator. If you have lots of luggage you may struggle getting it all up the stairs, also in the apartment there is a closet to hang some clothes but there isn't a chest of drawers to store other clothes.
One evening we heard noise from the street late into the night (actually well into the morning) but that's what you get from being in a great location.
The apartment was very comfortable, but if you plan to cook you will find that the kitchen is very small. If you are only having coffee or snacks in the apartment then it's fine.
Overall we really enjoyed our stay at the apartment and would recommend it.