I have an older dial one (guess they are "first generation" now) and it was always right on to our very accurate home scale (legal for trade grade, not bed bath and beyond grade).
In reality though the scale that matters is the one you put the bag on, I've actually seen a check in person move a 50.4 lb suitcase to the scale at the next check in area (just slide it over) where it weighed 49.6 and went through for free.
What the airports need to do is have a scale way before the counter that people who want to move stuff around can use. I saw one in one airport, not a giant platform one like they have at the counter, but a shipping scale with the head mounted on the wall to make it easy, sort of like the sizers do for carry ons.