I currently live in Portland.
It’s a great place to visit in summer. Not a bad place to visit in early Autumn. Not worth visiting as a tourist any other time of the year unless you love skiing or snowshoeing.
But I don’t think it is a destination, more a base camp. There is plenty to do in the city to fill a day or two, but you will really want to get down to Boston (which I also lived in for a few years before moving here), up to Acadia, and even further up to Montreal/Quebec City, whilst you are here.
Happy to offer any other advice if you have any specific questions.