Maine gets a few million visitors a year.
As with anything else, it depends on what you want.
If you want to ride a 100km in the Italian alps and sit on a table outside with a gorgeous view and an espresso, we're not your cup of joe. And I think italy is one of the best places on the planet to ride a bike (except Rome).
Anyway, we have lots of places. Baxter is the end of the AT, and terrific. There's Acadia, and good road and mtn riding, and you can rent. We have really good restaurants. We also have really good ice cream. We have some cool islands. We have some good bike rides, but you have to be careful, because there are a lot of roads I would not suggest you ride. Perhaps my favorite place to stop on a bike ride is Camden, but getting in and out is tricky.
We also have a few LL Bean factory stores. They are catch as catch can, but I get some great deals there.
For my 2 cents, the best place to stay in Maine is near Augusta, and there is a lot of tough hilly riding there. We used to do that occasionally. One of the rooms has a hot tub. They do catering, and usually tell you to hit the fridge, their goodies are awesome, and after riding all day, better than awesome.
There is really good riding the North Conway NH area, and we liked Vermont as well.