Reloading is a hobby for me, it just happens to feed another hobby. I'm not a high volume reloader, so a beam scale works fine for me. The web cam and old lap top computer sure makes it easier on my neck.
I have a green three poise 505 that I bought back in the 80's, two M5's, a beautiful creme and red 505 with the large pan and a D5. The green 505 is the one I use, it'll react to one grain of Varget, it repeats and always check dead on with the check weights. The D5 is my second choice, it just takes longer to dampen.
The other three don't repeat. I've removed and cleaned the bearings, lightly stoned the knife edges, made sure the cradle is centered and cleaned the beams and they still don't repeat like the 505 and D5. All of my scales have had the same treatment.