We don't have much criteria - just a looking for a nice home, maybe on the water or with a view and reasonable taxes. Access to good sailing is important but that doesn't rule out much on coastal Maine as far as we can tell...
When contemplating a move to Maine I would suggest the following:
1. Rent before you buy to be certain that the winter climate is to your liking. True anywhere, but especially in a location where the winters are long and cold.
2. Investigate the tax situation. The income tax in Maine is very progressive and high. If you have a reasonable income and relocate from a low or medium income tax state, you will be shocked at the level in Maine.
3. If you are interested in waterfront property, investigate the property taxes as well. Likely to be much higher than non-waterfront.
Maine is beautiful in the summer but there are offsetting issues to be investigated.