We spent a week in Portland in the fall and loved it. Our favorites were Fore Street, Food Factory Miyake, the bagel place in South Portland, and the Five Islands Lobster Co. in Georgetown, ME. Each of these places were superlative. The sushi at Miyake was second only to Sushi Yasuda in NYC and much less expensive.
If you like beer, the Great Lost Bear is a local bar with a great selection.