My hubby and I went to Bar Harbor this June before the season officially opened. The highlight of our trip was a beer brewery tour and tasting at Atlantic Coast brewing and LLBean in Freeport. Other than that Hurricane Barry socked us in with fog and rain so none of the activities we booked were running and we got food poisoning..
I have a coworker who loves Maine and he is and wife try to get there every year to hike and kayak. There are tons or outlets in Freeport if you like shopping and Bar Harbor has lots of outdoor activities if you get nice weather. You can always take the ferry to Nova Scotia or Newfoundland. I plan to return when I forget about the food poisoning.
Depending on where you are travelling there from we stopped in Gloucester, Mass for a whale watch and staying in a B&B on the coast in Rockport, Mass. There is also Boston and all the historical places surrounding.
Overall I love New England.