Obviously (probably) nobody on this list besides BlackSlax has been up and down US 1 the last three years than me. I was stopped twice in that time, once on the bottom end just north of Houlton, and once in Presque Isle. I was let go with a warning both times.
Like the man said, the speed limits are because the road goes through small towns with private homes (read Kids) close on the road. You'll go from 55 to 35 and less, most notably in P.I., very quickly. Decelerating that fast, especially if you have a load/trailer and were already over 55, is a task, at least.
I would not characterize these situations as speed traps in the classic sense as much as maybe something you might not be prepared for after running 80ish on the Maine Turnpike for 4 hours.
Enjoy US1, don't miss "The Planets/Solar system" roadside the length of the trek.
Bob W, PR Guy LTA