In the book "The Crucible" what do other characters think about John and Elizabeth Procter's relationship?

That's an interesting question. Relationships in Puritan societies at this time were anything but romantic. So how others in the town saw it would not be the same as how we see it. These unions were forged out of family arrangements and functioned out of a necessity for survival rather than romantic love. Certainly Abigail, living in the house, could see the distance between the two. Abigail takes advantage of this through her tryst with John. I don't see the other villagers as really caring that much. Their relationships were likely not that much different.

Also I should add by the end of the novel there is more of a bond between the two. John's indiscretions and Abigail's accusations brought them together on a level that transcended anything they might have had before. This would have been evident to the townspeople.