From our experience cruising the Northeast, moving South to North:
1. There's only one choice in Nantucket - the Boat Basin. Very nice, very upscale, very expensive.
2. The Black Dog on MV is OK, walking distance to most things, expensive.
3. The town dock at Marblehead is awesome, very inexpensive, walking distance to most things, terrific facilities.
4. Kennebec Tavern and Marina in Bath is great (my hometown, make sure you say hi), then take the inside passage to Boothbay Harbor where there's lots of choices.
5. There's no real facilities in New Harbor, but dock at Shaw's restaurant and buy a beer for the lobsterman sitting next to you at the bar. He'll set you up with a mooring for the night. Beautiful harbor, quiet, great food at Shaw's.
6. The town dock at Northeast Harbor is also awesome, very inexpensive, very quiet, walking distance to most things, terrific facilities.
7. Avoid Bar Harbor, nothing interesting to see other than tourist traps, poor facilities.
That my report. Let me know if we can be of any other help. If you'd like to do any fishing while you're up this way I'd be happy to join you.
Larry