I'm in Damariscotta and check Fi availability occasionally. It has not been available since I heard about it. If you can get it, it will probably be great because US Cellular has always had great coverage in the area.

I know everyone hates the company, but I use Spectrum Mobile. It's similar to Fi, uses Verizon towers (a close second in coverage), and I pay $59/mo for two lines: one unlimited, one 1GB. It's a great price because we don't need much.