Granted my bedroom has ceiling fan, but I'm afraid that alone won't be enough, because it will most likely be upper 80s or hotter in the upstairs bedroom at night should the central AC fail in summer.
When central AC is working normally, as an added benefit, I suppose the portable may also be useful for purpose of cooling the bedroom at night by a few degrees without my having to lower the thermostat for the entire house.
I already have a portable AC for the home office (also upstairs), since that room has a cooling problem. I realize the portables on wheels don't work as well as window units due to negative pressure, but at night when the outside temperature is cooler they generally work well. Window units can't be installed here though.