A good electronic scale is a must have. However the Lee can be adjusted and zeroed to work fine. I used these types for years before buying an electronic scale.
I have an Ohaus 10-10 Balance Scale (mechanical) that I've been using for the last 35+yrs. I use a set of Lyman Calibration weights to check it everytime I use it. Depending on what I'm loading determines the Calibration weight I use. Usually the 10 grain weight for Pistol cart. and the 15 or 20 grain for Rifle cart.. I got to admit that I'm curious about the Electronic Scales. But then "if it ain't broke don't fix it".