Portland is the epicenter of high-end restaurants, awesome things going on there. While summer is the busy season, it's not a ghost town in winter by any means. It has a lively year-round community (biggest city in the state) that has a good amount of money and a trendy lifestyle (hipsters, high-end clothing stores, ipads everywhere etc.). Many Boston chefs are relocating to Portland or getting their start there and going to Boston. This is where you want to be.
Outside of Portland there are some bright spots like Ogunquit (arrows restaurant there is worthy of a michelin star) Rockland (primo restaurant owner there just one a james beard award for best chef) and couple others in between. Also many resorts and high-end inns in the touristy coastal areas. Winter also attracts some business in these sort of resort places too but these are obviously seasonal for the most part.